diff --git a/hack/check-docker-image/check_mysql.sh b/hack/check-docker-image/check_mysql.sh
deleted file mode 100755
index d4a7906b..00000000
--- a/hack/check-docker-image/check_mysql.sh
+++ /dev/null
@@ -1,44 +0,0 @@
-#!/bin/sh
-
-DIR=$(cd $(dirname $0); pwd)
-OPTUNA_DASHBOARD_IMAGE=${OPTUNA_DASHBOARD_IMAGE:-cbata/optuna-dashboard}
-
-echo ""
-echo "1. Prepare MYSQL 8.0 Server using Docker."
-echo ""
-
-set -e
-docker run \
-  -d \
-  --rm \
-  -p 3306:3306 \
-  -e MYSQL_USER=optuna \
-  -e MYSQL_DATABASE=optuna \
-  -e MYSQL_PASSWORD=password \
-  -e MYSQL_ALLOW_EMPTY_PASSWORD=yes \
-  --name optuna-mysql \
-  mysql:8
-
-echo "Wait ready for MySQL"
-sleep 20
-
-
-echo ""
-echo "2. Run an Optuna example."
-echo ""
-
-python ${DIR}/optuna_example.py "mysql+pymysql://optuna:password@127.0.0.1:3306/optuna"
-
-set +e
-
-echo ""
-echo "3. Open Web Dashboard"
-echo ""
-
-docker run -it --rm -p 8080:8080 --link=optuna-mysql $OPTUNA_DASHBOARD_IMAGE "mysql+pymysql://optuna:password@optuna-mysql:3306/optuna"
-
-echo ""
-echo "4. Stop MYSQL Server"
-echo ""
-
-docker stop optuna-mysql
diff --git a/hack/check-docker-image/check_postgres.sh b/hack/check-docker-image/check_postgres.sh
deleted file mode 100755
index 8a7d60e7..00000000
--- a/hack/check-docker-image/check_postgres.sh
+++ /dev/null
@@ -1,43 +0,0 @@
-#!/bin/sh
-
-DIR=$(cd $(dirname $0); pwd)
-OPTUNA_DASHBOARD_IMAGE=${OPTUNA_DASHBOARD_IMAGE:-cbata/optuna-dashboard}
-
-echo ""
-echo "1. Run PostgreSQL Server using Docker."
-echo ""
-
-set -e
-docker run \
-  -d \
-  --rm \
-  -p 5432:5432 \
-  -e POSTGRES_USER=optuna \
-  -e POSTGRES_DB=optuna \
-  -e POSTGRES_PASSWORD=password \
-  --name optuna-postgres \
-  postgres:10.1-alpine
-
-echo "Wait ready for PostgreSQL"
-sleep 20
-
-
-echo ""
-echo "2. Run an Optuna example."
-echo ""
-
-python ${DIR}/optuna_example.py "postgresql+psycopg2://optuna:password@127.0.0.1:5432/optuna"
-
-set +e
-
-echo ""
-echo "3. Open Web Dashboard"
-echo ""
-
-docker run -it --rm -p 8080:8080 --link=optuna-postgres $OPTUNA_DASHBOARD_IMAGE "postgresql+psycopg2://optuna:password@optuna-postgres:5432/optuna"
-
-echo ""
-echo "4. Stop MYSQL Server"
-echo ""
-
-docker stop optuna-postgres
diff --git a/hack/check-docker-image/optuna_example.py b/hack/check-docker-image/optuna_example.py
deleted file mode 100644
index 66cda2df..00000000
--- a/hack/check-docker-image/optuna_example.py
+++ /dev/null
@@ -1,19 +0,0 @@
-import sys
-
-import optuna
-
-
-def objective(trial):
-    x = trial.suggest_float("x", -100, 100)
-    y = trial.suggest_categorical("y", [-1, 0, 1])
-    return x**2 + y
-
-
-if __name__ == "__main__":
-    if len(sys.argv) != 2:
-        print("Invalid args")
-        sys.exit(1)
-
-    db_url = sys.argv[1]
-    study = optuna.create_study(storage=db_url, study_name="example-study")
-    study.optimize(objective, n_trials=10)