diff --git a/.github/workflows/license.yml b/.github/workflows/license.yml
new file mode 100644
index 00000000..96e3d924
--- /dev/null
+++ b/.github/workflows/license.yml
@@ -0,0 +1,21 @@
+name: license
+
+on:
+  push:
+    branches: [ master ]
+    paths-ignore: '**.md'
+  pull_request:
+    branches: [ master ]
+    paths-ignore: '**.md'
+
+jobs:
+  license_check:
+    name: License check
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check license
+        run: |
+          find include/small_gicp src/small_gicp -type f | xargs -I filename bash -c 'if ! grep -q SPDX-License-Identifier filename; then echo filename : lisence not found; exit 1; fi'
\ No newline at end of file
diff --git a/include/small_gicp/ann/flat_container.hpp b/include/small_gicp/ann/flat_container.hpp
index 4f0b4bdf..f16bde37 100644
--- a/include/small_gicp/ann/flat_container.hpp
+++ b/include/small_gicp/ann/flat_container.hpp
@@ -1,3 +1,5 @@
+// SPDX-FileCopyrightText: Copyright 2024 Kenji Koide
+// SPDX-License-Identifier: MIT
 #pragma once
 
 #include <queue>
diff --git a/include/small_gicp/ann/knn_result.hpp b/include/small_gicp/ann/knn_result.hpp
index 757ab8db..53ee3756 100644
--- a/include/small_gicp/ann/knn_result.hpp
+++ b/include/small_gicp/ann/knn_result.hpp
@@ -1,3 +1,5 @@
+// SPDX-FileCopyrightText: Copyright 2024 Kenji Koide
+// SPDX-License-Identifier: MIT
 #pragma once
 
 #include <array>
diff --git a/include/small_gicp/factors/robust_kernel.hpp b/include/small_gicp/factors/robust_kernel.hpp
index 0b27d546..9af6a8a5 100644
--- a/include/small_gicp/factors/robust_kernel.hpp
+++ b/include/small_gicp/factors/robust_kernel.hpp
@@ -1,3 +1,5 @@
+// SPDX-FileCopyrightText: Copyright 2024 Kenji Koide
+// SPDX-License-Identifier: MIT
 #pragma once
 
 #include <Eigen/Core>