diff --git a/optuna/importance/__init__.py b/optuna/importance/__init__.py
index a2744916ec..2314ef9329 100644
--- a/optuna/importance/__init__.py
+++ b/optuna/importance/__init__.py
@@ -65,10 +65,11 @@ def get_param_importances(
             :class:`~optuna.importance.FanovaImportanceEvaluator`.
 
             .. note::
-                This class takes over 1 minute when given a study that contains 1000+ trials.
-                We published `optuna-fast-fanova <https://github.com/optuna/optuna-fast-fanova>`_ library,
-                that is a Cython accelerated fANOVA implementation. By using it, you can get hyperparameter
-                importances within a few seconds.
+                :class:`~optuna.importance.FanovaImportanceEvaluator` takes over 1 minute
+                when given a study that contains 1000+ trials. We published
+                `optuna-fast-fanova <https://github.com/optuna/optuna-fast-fanova>`_ library,
+                that is a Cython accelerated fANOVA implementation.
+                By using it, you can get hyperparameter importances within a few seconds.
 
         params:
             A list of names of parameters to assess.
diff --git a/optuna/visualization/_param_importances.py b/optuna/visualization/_param_importances.py
index cd8bef3d4c..04b4bf526b 100644
--- a/optuna/visualization/_param_importances.py
+++ b/optuna/visualization/_param_importances.py
@@ -115,10 +115,11 @@ def objective(trial):
             :class:`~optuna.importance.FanovaImportanceEvaluator`.
 
             .. note::
-                This class takes over 1 minute when given a study that contains 1000+ trials.
-                We published `optuna-fast-fanova <https://github.com/optuna/optuna-fast-fanova>`_ library,
-                that is a Cython accelerated fANOVA implementation. By using it, you can get hyperparameter
-                importances within a few seconds.
+                :class:`~optuna.importance.FanovaImportanceEvaluator` takes over 1 minute
+                when given a study that contains 1000+ trials. We published
+                `optuna-fast-fanova <https://github.com/optuna/optuna-fast-fanova>`_ library,
+                that is a Cython accelerated fANOVA implementation.
+                By using it, you can get hyperparameter importances within a few seconds.
 
         params:
             A list of names of parameters to assess.