diff --git a/app/controllers/documents_controller.rb b/app/controllers/documents_controller.rb
index b857caa0..39e9d69d 100644
--- a/app/controllers/documents_controller.rb
+++ b/app/controllers/documents_controller.rb
@@ -3,34 +3,15 @@ class DocumentsController < ApplicationController
   before_action :set_document, only: %i[ show edit update destroy ]
   protect_from_forgery :except => [:api_markdown]
 
-  def search_check(param)
-    if param.present?
-      key_words = param.split(/[\p{blank}\s]+/)
-      grouping_hash = key_words.reduce({}) {|hash, word| hash.merge(word => {content_or_creator_screen_name_or_description_or_project_name_or_location_cont: word})}
-    else
-      nil
-    end
-  end
-
-  def sort_check(param)
-    if param.present?
-      sort_column = []
-      sort_column << param
-    else
-      "start_at DESC"
-    end
-  end
-
   # GET /documents or /documents.json
   def index
-    if params[:q].nil?
-      @q = Document.ransack(params[:q])
-      @q.sorts = "start_at DESC"
-    else
-      @q = Document.ransack({combinator: 'and', groupings: search_check(params[:q][:content_or_creator_screen_name_or_description_or_project_name_or_location_cont])})
-      @q.sorts = sort_check(params[:q][:s])
-    end  
-    @documents = @q.result.page(params[:page]).per(50).includes(:user)
+    search_query = { combinator: "and", groupings: split_into_search_queries(params.dig(:q, :text_cont)) }
+    search_query.merge!({ tags_id_eq: params[:tag_id] }) if params[:tag_id].present?
+
+    @q = Document.ransack(search_query)
+    @q.sorts = build_sort_query_with_default(params.dig(:q, :s))
+    @documents = @q.result.page(params[:page]).per(50).includes(:user, :creator, :project, :tags)
+    @tags = Tag.all
   end
 
   # GET /documents/1 or /documents/1.json
@@ -130,4 +111,26 @@ def parse_tag_names(tag_names)
     end
   end
 
+  # Build ransack AND search query from params
+  # Example: { text_cont: "foo bar" } => [{ text_cont: "foo" }, { text_cont: "bar" }]
+  def split_into_search_queries(param)
+    return nil if param.nil? || param.blank?
+
+    # Split keyword and build AND search condition
+    queries = []
+    words = param.split(/[\p{blank}\s]+/)
+    words.each do |word|
+      queries << { text_cont: word }
+    end
+
+    queries
+  end
+
+  def build_sort_query_with_default(param)
+    if param.present?
+      param
+    else
+      "start_at DESC"
+    end
+  end
 end
diff --git a/app/controllers/tasks_controller.rb b/app/controllers/tasks_controller.rb
index 84b7176d..a3eb0af7 100644
--- a/app/controllers/tasks_controller.rb
+++ b/app/controllers/tasks_controller.rb
@@ -3,43 +3,22 @@ class TasksController < ApplicationController
   before_action :set_task, only: %i[ show edit update destroy ]
   before_action :get_form_data, only: %i[ new edit ]
 
-  def search_check(param)
-    if param.present?
-      key_words = param.split(/[\p{blank}\s]+/)
-      grouping_hash = key_words.reduce({}) { |hash, word| hash.merge(word => { content_or_assigner_screen_name_or_description_or_project_name_cont: word }) }
-    else
-      nil
-    end
-  end
-
-  def sort_check(param)
-    if param.present?
-      sort_column = []
-      sort_column << "state.priority DESC" << param
-    else
-      "state.priority DESC"
-    end
-  end
-
   # GET /tasks or /tasks.json
   def index
-    if params[:q].nil?
-      @q = Task.joins(:state).ransack(params[:q])
-      @q.sorts = ["state.priority DESC", "due_at ASC"]
-    else
-      @q = Task.joins(:state).ransack({combinator: 'and', groupings: search_check(params[:q][:content_or_assigner_screen_name_or_description_or_project_name_cont])})
-      @q.sorts = sort_check(params[:q][:s])
-    end
+    search_query = { combinator: "and", groupings: split_into_search_queries(params.dig(:q, :text_cont)) }
 
-    @show_all = params[:all] == 'true'
-    tasks_query = @q.result
+    session[:show_all] = params[:all] == 'true' if params[:all].present?
+    search_query.merge!({ assigner_id_eq: current_user.id }) unless session[:show_all]
 
-    if params[:only_todo] == '1'
-      tasks_query = tasks_query.merge(Task.active)
-    end
-    
-    tasks_query = tasks_query.joins(:user).where(users: {screen_name: current_user&.screen_name}) unless @show_all
-    @tasks = tasks_query.page(params[:page]).per(50).includes(:user, :state)
+    session[:only_todo] = params[:only_todo] if params[:only_todo].present?
+    search_query.merge!({ task_state_id_eq: TaskState.where(name: "todo").first.id }) if session[:only_todo] == "1"
+
+    search_query.merge!({ tags_id_eq: params[:tag_id] }) if params[:tag_id].present?
+
+    @q = Task.ransack(search_query)
+    @q.sorts = build_sort_query_with_default(params.dig(:q, :s))
+    @tasks = @q.result.page(params[:page]).per(50).includes(:user, :project, :tags, :assigner, :state)
+    @tags = Tag.all
   end
 
   # GET /tasks/1 or /tasks/1.json
@@ -136,4 +115,29 @@ def parse_tag_names(tag_names)
       tag ? tag : Tag.create(name: tag_name)
     end
   end
+
+  # Build ransack AND search query from params
+  # Example: { text_cont: "foo bar" } => [{ text_cont: "foo" }, { text_cont: "bar" }]
+  def split_into_search_queries(param)
+    return nil if param.nil? || param.blank?
+
+    # Split keyword and build AND search condition
+    queries = []
+    words = param.split(/[\p{blank}\s]+/)
+    words.each do |word|
+      queries << { text_cont: word }
+    end
+
+    queries
+  end
+
+  def build_sort_query_with_default(param)
+    query = ["state_priority DESC"]
+    if param.present?
+      query << param
+    else
+      query << "due_at ASC"
+    end
+    query
+  end
 end
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index 163290b9..8b99c224 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -2,4 +2,12 @@ module ApplicationHelper
   def tag_label(tag)
     raw %(<span class="inline-block bg-blue-500 hover:bg-blue-700 text-white font-bold py-2 px-0 rounded"> #{tag.name}</span>)
   end
+
+  def url_with_query(url, key, value)
+    uri = URI(url)
+    query = Rack::Utils.parse_query(uri.query)
+    query[key] = value
+    uri.query = query.to_query
+    uri.to_s
+  end
 end
diff --git a/app/helpers/documents_helper.rb b/app/helpers/documents_helper.rb
index 242b4fce..8900fb76 100644
--- a/app/helpers/documents_helper.rb
+++ b/app/helpers/documents_helper.rb
@@ -1,2 +1,15 @@
 module DocumentsHelper
+  def preserve_other_params(except: [])
+    forms = []
+    params.except(:controller, :action, :commit, *except).each do |key, value|
+      if key == 'q'
+        value.each do |q_key, q_value|
+          forms << hidden_field_tag("q[#{q_key}]", q_value)
+        end
+      else
+        forms << hidden_field_tag(key, value)
+      end
+    end
+    forms.join.html_safe
+  end
 end
diff --git a/app/helpers/tasks_helper.rb b/app/helpers/tasks_helper.rb
index 1e5645f6..b153400b 100644
--- a/app/helpers/tasks_helper.rb
+++ b/app/helpers/tasks_helper.rb
@@ -7,4 +7,19 @@ def days_to_deadline_as_string(task)
       ""
     end
   end
+
+  def preserve_other_params(except: [])
+    forms = []
+    params.except(:controller, :action, :commit, *except).each do |key, value|
+      if key == 'q'
+        value.each do |q_key, q_value|
+          forms << hidden_field_tag("q[#{q_key}]", q_value)
+        end
+      else
+        forms << hidden_field_tag(key, value)
+      end
+    end
+    p forms
+    forms.join.html_safe
+  end
 end
diff --git a/app/models/document.rb b/app/models/document.rb
index 6ecc5f1c..9d461bfd 100644
--- a/app/models/document.rb
+++ b/app/models/document.rb
@@ -14,8 +14,10 @@ class Document < ApplicationRecord
   #validates :project, presence: true
   before_validation :add_unique_action_item_marker
 
+  ransack_alias :text, :content_or_creator_screen_name_or_description_or_project_name_or_location_cont
+
   def self.ransackable_attributes(auth_object = nil)
-    ["content", "created_at", "creator_id", "description", "end_at", "id", "location", "project_id", "start_at", "updated_at"]
+    ["content", "created_at", "creator_id", "description", "end_at", "id", "location", "project_id", "start_at", "updated_at", "text"]
   end
 
   def self.ransackable_associations(auth_object = nil)
diff --git a/app/models/tag.rb b/app/models/tag.rb
index 54280602..2a690828 100644
--- a/app/models/tag.rb
+++ b/app/models/tag.rb
@@ -5,6 +5,10 @@ class Tag < ApplicationRecord
   has_many :documents, through: :document_tags, dependent: :restrict_with_exception
   validates :name, presence: true, uniqueness: true
 
+  def self.ransackable_attributes(auth_object = nil)
+    [ "id", "name" ]
+  end
+
   def self.order_by_popularity
     self.find_by_sql <<~'SQL'
       SELECT
diff --git a/app/models/task.rb b/app/models/task.rb
index 0002e1d4..24478ea9 100644
--- a/app/models/task.rb
+++ b/app/models/task.rb
@@ -15,9 +15,11 @@ class Task < ApplicationRecord
 
   validates :content, presence: true
 
+  ransack_alias :text, :content_or_assigner_screen_name_or_description_or_project_name
+
   def self.ransackable_attributes(auth_object = nil)
-    [ "assigner_id", "content", "created_at", "creator_id", "description", "due_at", "id", "project_id", "tag_id", "task_state_id", "updated_at" ]
-    end
+    [ "assigner_id", "content", "created_at", "creator_id", "description", "due_at", "id", "project_id", "tag_id", "task_state_id", "updated_at", "text" ]
+  end
 
   def self.ransackable_associations(auth_object = nil)
     [ "assigner", "project", "state", "tags", "task_tags", "user" ]
diff --git a/app/views/documents/index.html.erb b/app/views/documents/index.html.erb
index c15f2f02..86ebde80 100644
--- a/app/views/documents/index.html.erb
+++ b/app/views/documents/index.html.erb
@@ -1,3 +1,7 @@
+<% content_for :tag_list do %>
+  <%= render partial: "layouts/tag_list", locals: { base_link: request.original_url } %>
+<% end %>
+
 <div class="d-flex align-items-center">
   <%= render 'layouts/h1', title: "文書一覧" %>
   <div class="flex-grow-1"></div>
@@ -18,10 +22,11 @@
 
   <div class="border p-3 my-3 rounded d-flex align-items-center gap-3">
     <%= search_form_for @q, class: "d-flex align-items-center w-100" do |f| %>
-      <%= f.text_field :content_or_creator_screen_name_or_description_or_project_name_or_location_cont, 
-        class: "form-control me-2", 
-        placeholder: '検索ワードを入力して下さい', 
+      <%= f.text_field :text_cont,
+        class: "form-control me-2",
+        placeholder: '検索ワードを入力して下さい',
         style: "flex: 1;" %>
+      <%= preserve_other_params(except: [:q]) %>
       <%= f.submit "検索", class: "btn btn-primary" %>
     <% end %>
   </div>
diff --git a/app/views/layouts/_tag_list.html.erb b/app/views/layouts/_tag_list.html.erb
index 27460f70..97a7c254 100644
--- a/app/views/layouts/_tag_list.html.erb
+++ b/app/views/layouts/_tag_list.html.erb
@@ -1,8 +1,11 @@
-<div class="border mx-auto p-3 overflow-auto">
-  <p class="fw-bold fs-4 mb-3">タグ一覧</p>
-  <div class="d-flex flex-wrap gap-1">
-    <% Tag.order_by_popularity.each do |tag| %>
-      <%= link_to tag_label(tag), tag, class: "btn btn-primary btn-outline-primary" %>
-    <% end %>
+<aside class="col-md-3 p-3">
+  <div class="border mx-auto p-3 overflow-auto">
+    <p class="fw-bold fs-4 mb-3">タグ一覧</p>
+    <div class="d-flex flex-wrap gap-1">
+      <% Tag.order_by_popularity.each do |tag| %>
+        <% link = base_link.present? ? url_with_query(base_link, "tag_id", tag.id) : tag_path(tag) %>
+        <%= link_to tag_label(tag), link, class: "btn btn-primary btn-outline-primary" %>
+      <% end %>
+    </div>
   </div>
-</div>
+</aside>
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index aa1d1e61..ff012b05 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -37,9 +37,7 @@
 
     <div class="container-fluid">
       <div class="row">
-        <aside class="col-md-3 p-3">
-          <%= render 'layouts/tag_list' %>
-        </aside>
+        <%= yield :tag_list %>
 
         <main class="col-md-9">
           <div class="container p-5">
diff --git a/app/views/tasks/index.html.erb b/app/views/tasks/index.html.erb
index 7ecd5db3..900a9934 100644
--- a/app/views/tasks/index.html.erb
+++ b/app/views/tasks/index.html.erb
@@ -1,3 +1,7 @@
+<% content_for :tag_list do %>
+  <%= render partial: "layouts/tag_list", locals: { base_link: request.original_url } %>
+<% end %>
+
 <div class="d-flex align-items-center">
   <%= render 'layouts/h1', title: "タスク一覧" %>
   <div class="flex-grow-1"></div>
@@ -18,11 +22,11 @@
 
   <div class="border p-3 my-3 rounded d-flex align-items-center gap-3">
     <%= search_form_for @q, class: "d-flex align-items-center w-100" do |f| %>
-      <%= f.text_field :content_or_assigner_screen_name_or_description_or_project_name_cont, 
-        class: "form-control me-2", 
-        placeholder: '検索ワードを入力して下さい', 
+      <%= f.text_field :text_cont,
+        class: "form-control me-2",
+        placeholder: '検索ワードを入力して下さい',
         style: "flex: 1;" %>
-      <%= hidden_field_tag :only_todo, params[:only_todo] if params[:only_todo].present? %>
+      <%= preserve_other_params(except: [:q]) %>
       <%= f.submit "検索", class: "btn btn-primary" %>
     <% end %>
   </div>
@@ -31,25 +35,25 @@
 </div>
 
 <%= form_with url: request.path, method: :get, local: true, html: { class: "d-flex" } do %>
-  <%= check_box_tag :only_todo, "1", params[:only_todo] == "1", onchange: "this.form.submit()" %>
+  <%= preserve_other_params(except: [:only_todo]) %>
+  <%= hidden_field_tag :only_todo, session[:only_todo] == '1' ? '0' : '1' %>
+  <%= check_box_tag "", "", checked: session[:only_todo] == "1", onchange: "this.form.submit()" %>
   <div class="mx-1">
     todoのみ
   </div>
-
-  <% if params[:q].present? %>
-    <% params[:q].each do |key, value| %>
-      <%= hidden_field_tag "q[#{key}]", value %>
-    <% end %>
-  <% end %>
 <% end %>
 
-<% current_q_params = request.query_parameters.except(:controller, :action, :page) %>
 <ul class="text-center nav nav-tabs" role="tablist">
   <li class="nav-item w-50 bg-light">
-    <%= link_to "#{current_user&.screen_name}のタスク", tasks_path(current_q_params.merge(all: 'false')), class: "nav-link #{'active' if !@show_all} link-text" %>
+    <%= link_to "#{current_user&.screen_name}のタスク",
+        url_with_query(request.original_url, "all", "false"),
+        class: "nav-link #{'active' if !session[:show_all]} link-text" %>
   </li>
+
   <li class="nav-item w-50 bg-light">
-    <%= link_to 'すべてのタスク', tasks_path(current_q_params.merge(all: 'true')), class: "nav-link #{'active' if @show_all} link-text" %>
+    <%= link_to 'すべてのタスク',
+        url_with_query(request.original_url, "all", "true"),
+        class: "nav-link #{'active' if session[:show_all]} link-text" %>
   </li>
 </ul>
 
@@ -58,7 +62,7 @@
     <%= render @tasks %>
     <div class="row">
       <div class="col-md-12 col-sm-12 text-center hidden-xs">
-        <%= raw(paginate @tasks, params: current_q_params) %>
+        <%= raw(paginate @tasks) %>
       </div>
     </div>
   </div>