diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a2ec4a65..aec1d535 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       # panic! を Ubuntu 上で評価するとバックトレースが表示されてしまう問題の修正
       - name: set environment variable
@@ -39,7 +39,7 @@ jobs:
     if: github.ref == 'refs/heads/main'
     steps:
       - name: checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: lean action
         uses: leanprover/lean-action@v1
diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 76b93f6c..3b5a5bbb 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Install elan
         run: |
diff --git a/.github/workflows/devcontainer.yml b/.github/workflows/devcontainer.yml
index 2ca907aa..6932a962 100644
--- a/.github/workflows/devcontainer.yml
+++ b/.github/workflows/devcontainer.yml
@@ -22,7 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Set up Node.js
         uses: actions/setup-node@v6
diff --git a/.github/workflows/update.yml b/.github/workflows/update.yml
index c704541e..e765ed52 100644
--- a/.github/workflows/update.yml
+++ b/.github/workflows/update.yml
@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       # panic! を Ubuntu 上で評価するとバックトレースが表示されてしまう問題の修正
       - name: set environment variable
         run: echo "LEAN_BACKTRACE=0" >> $GITHUB_ENV