diff --git a/optuna_dashboard/_app.py b/optuna_dashboard/_app.py
index caf2be02..65a5bb00 100644
--- a/optuna_dashboard/_app.py
+++ b/optuna_dashboard/_app.py
@@ -249,19 +249,17 @@ def create_app(storage: BaseStorage, debug: bool = False) -> Bottle:
             return {"reason": "You need to set study_name and direction"}
 
         try:
-            study_id = storage.create_new_study(study_name)
+            study_id = storage.create_new_study(
+                study_name,
+                directions=[
+                    StudyDirection.MAXIMIZE if d.lower() == "maximize" else StudyDirection.MINIMIZE
+                    for d in directions
+                ],
+            )
         except DuplicatedStudyError:
             response.status = 400  # Bad request
             return {"reason": f"'{study_name}' is already exists"}
 
-        storage.set_study_directions(
-            study_id,
-            [
-                StudyDirection.MAXIMIZE if d.lower() == "maximize" else StudyDirection.MINIMIZE
-                for d in directions
-            ],
-        )
-
         summary = get_study_summary(storage, study_id)
         if summary is None:
             response.status = 500  # Internal server error
diff --git a/python_tests/test_api.py b/python_tests/test_api.py
index 5a795c71..ead1ffc0 100644
--- a/python_tests/test_api.py
+++ b/python_tests/test_api.py
@@ -2,6 +2,7 @@ import json
 from unittest import TestCase
 
 import optuna
+from optuna.study import StudyDirection
 from optuna import get_all_study_summaries
 from optuna_dashboard._app import create_app
 
@@ -16,8 +17,8 @@ def objective(trial: optuna.trial.Trial) -> float:
 class APITestCase(TestCase):
     def test_get_study_summaries(self) -> None:
         storage = optuna.storages.InMemoryStorage()
-        storage.create_new_study("foo1")
-        storage.create_new_study("foo2")
+        storage.create_new_study(study_name="foo1", directions=[StudyDirection.MINIMIZE])
+        storage.create_new_study(study_name="foo2", directions=[StudyDirection.MINIMIZE])
 
         app = create_app(storage)
         status, _, body = send_request(
@@ -126,7 +127,7 @@ class APITestCase(TestCase):
 
     def test_create_study_duplicated(self) -> None:
         storage = optuna.storages.InMemoryStorage()
-        storage.create_new_study("foo")
+        storage.create_new_study(study_name="foo", directions=[StudyDirection.MINIMIZE])
         self.assertEqual(len(get_all_study_summaries(storage)), 1)
 
         app = create_app(storage)
@@ -146,8 +147,8 @@ class APITestCase(TestCase):
 
     def test_delete_study(self) -> None:
         storage = optuna.storages.InMemoryStorage()
-        storage.create_new_study("foo1")
-        storage.create_new_study("foo2")
+        storage.create_new_study(study_name="foo1", directions=[StudyDirection.MINIMIZE])
+        storage.create_new_study(study_name="foo2", directions=[StudyDirection.MINIMIZE])
         self.assertEqual(len(get_all_study_summaries(storage)), 2)
 
         app = create_app(storage)