diff --git a/.github/workflows/python-tests.yml b/.github/workflows/python-tests.yml
index e1b320cc..c01e0161 100644
--- a/.github/workflows/python-tests.yml
+++ b/.github/workflows/python-tests.yml
@@ -21,7 +21,8 @@ jobs:
           python -m pip install --upgrade pip setuptools
           pip install --progress-bar off .[lint]
       - run: flake8 . --show-source
-      - run: black --check .
+      - run: black --check --diff .
+      - run: isort --check --diff .
       - run: mypy .
   test:
     runs-on: ubuntu-latest
diff --git a/DEVELOPMENT.md b/DEVELOPMENT.md
index bed40c4c..453c698b 100644
--- a/DEVELOPMENT.md
+++ b/DEVELOPMENT.md
@@ -76,6 +76,7 @@ $ tox -e py39
 $ pip install .[lint]
 $ flake8
 $ black --check .
+$ isort . --check
 $ mypy .
 ```
 
diff --git a/setup.cfg b/setup.cfg
index dc10a76f..1ae34112 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -35,6 +35,7 @@ install_requires =
 [options.extras_require]
 lint =
     black
+    isort
     mypy
     flake8
 
@@ -56,4 +57,15 @@ exclude = venv,build,.tox
 
 [mypy]
 ignore_missing_imports = True
-disallow_untyped_defs = True
\ No newline at end of file
+disallow_untyped_defs = True
+
+[isort]
+profile = black
+src_paths =
+    optuna_dashboard
+    tests
+line_length = 99
+lines_after_imports = 2
+force_single_line = True
+force_sort_within_sections = True
+order_by_type = False
diff --git a/tox.ini b/tox.ini
index fbe8bf5d..dd77fb99 100644
--- a/tox.ini
+++ b/tox.ini
@@ -6,6 +6,7 @@ envlist =
     py39
     flake8
     black
+    isort
     mypy
 
 [testenv:py36]
@@ -32,6 +33,10 @@ commands = flake8 . {posargs}
 deps = black
 commands = black --check . {posargs}
 
+[testenv:isort]
+deps = isort
+commands = isort . --check
+
 [testenv:mypy]
 deps = mypy
 commands = mypy . {posargs}