diff --git a/optuna_dashboard/_custom_plot_data.py b/optuna_dashboard/_custom_plot_data.py
index a4dfa4af..2ee04636 100644
--- a/optuna_dashboard/_custom_plot_data.py
+++ b/optuna_dashboard/_custom_plot_data.py
@@ -44,8 +44,8 @@ def objective(trial):
     Args:
         study:
             Target study object.
-        plot_data:
-            The plotly's graph object to save.
+        figure:
+            A :class:`plotly.graph_objects.Figure` object to save.
         graph_object_id:
             Unique identifier of the graph object. If specified, the graph object is overwritten.
             This must be a valid HTML id attribute value.