diff --git a/Scripts/my-script.sh b/Scripts/my-script.sh
index ca030f2..bbee2fc 100755
--- a/Scripts/my-script.sh
+++ b/Scripts/my-script.sh
@@ -2,22 +2,26 @@
 
 set -u
 
+function error_handler() {
+    echo "error=$(cat /tmp/Error)" >> "$GITHUB_OUTPUT"
+    exit 1
+}
+
 git config user.name 'Kazumasa Shimomura'
 git config user.email s2mr@users.noreply.github.com
 
-TARGET_BRANCH=$(echo "$COMMENT_BODY" | sed -e 's/\/ota --into \(.*\).*/\1/g')
+# 正規表現にマッチしない場合(e.g. --intoがない場合)はERRステータスになるので、
+# ERRのtrap はこれ以降で行う
+TARGET_BRANCH=$(expr "$COMMENT_BODY" : '.*--into \([^ ]*\)')
 
-if [ "$TARGET_BRANCH" != "" ]; then
-    git pull
-    git checkout "$TARGET_BRANCH"
-    git mmmmerge origin/"$PR_BRANCH" --no-rebase -m "[ota] Merge branch '$PR_BRANCH' into $TARGET_BRANCH" 2> /tmp/Error
+trap error_handler ERR
 
-    if [ "$(cat /tmp/Error)" != "" ]; then
-        echo "error=$(cat /tmp/Error)" >> "$GITHUB_OUTPUT"
-        exit 1
-    fi
+if [ "$TARGET_BRANCH" != "" ]; then
+    git pull 2> /tmp/Error
+    git checkout "$TARGET_BRANCH" 2> /tmp/Error
+    git merge origin/"$PR_BRANCH" --no-ff -m "[ota] Merge remote-tracking branch 'origin/$PR_BRANCH' into $TARGET_BRANCH" 2> /tmp/Error
 else
-    git commit --allow-empty -m "[ota]${COMMENT_BODY##/ota}"
+    git commit --allow-empty -m "[ota]${COMMENT_BODY##/ota}" 2> /tmp/Error
 fi
 
-git push
\ No newline at end of file
+git push