diff --git a/e2e_tests/test_dashboard/test_usecases/test_preferential_optimization.py b/e2e_tests/test_dashboard/test_usecases/test_preferential_optimization.py
index fa3317dc..0b19fea0 100644
--- a/e2e_tests/test_dashboard/test_usecases/test_preferential_optimization.py
+++ b/e2e_tests/test_dashboard/test_usecases/test_preferential_optimization.py
@@ -9,6 +9,7 @@ from playwright.sync_api import Page
 import pytest
 
 from ...test_server import make_test_server
+from ...utils import clear_inmemory_cache
 
 
 def make_test_storage() -> optuna.storages.InMemoryStorage:
@@ -43,6 +44,7 @@ def make_test_storage() -> optuna.storages.InMemoryStorage:
 
 @pytest.fixture
 def storage() -> optuna.storages.InMemoryStorage:
+    clear_inmemory_cache()
     storage = make_test_storage()
     return storage
 
diff --git a/e2e_tests/test_dashboard/test_usecases/test_study_history.py b/e2e_tests/test_dashboard/test_usecases/test_study_history.py
index 6c22b16b..f2d937bb 100644
--- a/e2e_tests/test_dashboard/test_usecases/test_study_history.py
+++ b/e2e_tests/test_dashboard/test_usecases/test_study_history.py
@@ -3,6 +3,7 @@ from playwright.sync_api import Page
 import pytest
 
 from ...test_server import make_test_server
+from ...utils import clear_inmemory_cache
 
 
 def make_test_storage() -> optuna.storages.InMemoryStorage:
@@ -23,6 +24,7 @@ def make_test_storage() -> optuna.storages.InMemoryStorage:
 
 @pytest.fixture
 def storage() -> optuna.storages.InMemoryStorage:
+    clear_inmemory_cache()
     storage = make_test_storage()
     return storage
 
diff --git a/e2e_tests/test_dashboard/visual_regression_test.py b/e2e_tests/test_dashboard/visual_regression_test.py
index ea6ff930..ab189343 100644
--- a/e2e_tests/test_dashboard/visual_regression_test.py
+++ b/e2e_tests/test_dashboard/visual_regression_test.py
@@ -5,10 +5,12 @@ from playwright.sync_api import Page
 import pytest
 
 from ..test_server import make_test_server
+from ..utils import clear_inmemory_cache
 
 
 @pytest.fixture
 def storage() -> optuna.storages.InMemoryStorage:
+    clear_inmemory_cache()
     storage = optuna.storages.InMemoryStorage()
     return storage
 
diff --git a/e2e_tests/utils.py b/e2e_tests/utils.py
new file mode 100644
index 00000000..68952ae9
--- /dev/null
+++ b/e2e_tests/utils.py
@@ -0,0 +1,9 @@
+from optuna_dashboard._storage import trials_cache
+from optuna_dashboard._storage import trials_cache_lock
+from optuna_dashboard._storage import trials_last_fetched_at
+
+
+def clear_inmemory_cache() -> None:
+    with trials_cache_lock:
+        trials_cache.clear()
+        trials_last_fetched_at.clear()