diff --git a/optuna_dashboard/ts/apiClient.ts b/optuna_dashboard/ts/apiClient.ts
index f1a7ad8c5..e618e21fc 100644
--- a/optuna_dashboard/ts/apiClient.ts
+++ b/optuna_dashboard/ts/apiClient.ts
@@ -5,7 +5,6 @@ import {
   FeedbackComponentType,
   FormWidgets,
   Note,
-  ParamImportance,
   PlotlyGraphObject,
   PreferenceFeedbackMode,
   PreferenceHistory,
@@ -113,7 +112,7 @@ export type UploadArtifactAPIResponse = {
 }
 
 export interface ParamImportancesResponse {
-  param_importances: ParamImportance[][]
+  param_importances: Optuna.ParamImportance[][]
 }
 
 export type PlotResponse = {
@@ -228,7 +227,9 @@ export abstract class APIClient {
     trialId: number,
     user_attrs: { [key: string]: number | string }
   ): Promise<void>
-  abstract getParamImportances(studyId: number): Promise<ParamImportance[][]>
+  abstract getParamImportances(
+    studyId: number
+  ): Promise<Optuna.ParamImportance[][]>
   abstract reportPreference(
     studyId: number,
     candidates: number[],
diff --git a/optuna_dashboard/ts/axiosClient.ts b/optuna_dashboard/ts/axiosClient.ts
index bb2b811ad..9b29f2db4 100644
--- a/optuna_dashboard/ts/axiosClient.ts
+++ b/optuna_dashboard/ts/axiosClient.ts
@@ -15,7 +15,6 @@ import {
 } from "./apiClient"
 import {
   FeedbackComponentType,
-  ParamImportance,
   StudyDetail,
   StudySummary,
   Trial,
@@ -230,7 +229,9 @@ export class AxiosClient extends APIClient {
       .then(() => {
         return
       })
-  getParamImportances = (studyId: number): Promise<ParamImportance[][]> =>
+  getParamImportances = (
+    studyId: number
+  ): Promise<Optuna.ParamImportance[][]> =>
     this.axiosInstance
       .get<ParamImportancesResponse>(
         `/api/studies/${studyId}/param_importances`
diff --git a/optuna_dashboard/ts/hooks/useParamImportance.ts b/optuna_dashboard/ts/hooks/useParamImportance.ts
index 9cddaafa4..e5baef6f0 100644
--- a/optuna_dashboard/ts/hooks/useParamImportance.ts
+++ b/optuna_dashboard/ts/hooks/useParamImportance.ts
@@ -1,8 +1,8 @@
+import * as Optuna from "@optuna/types"
 import { useQuery } from "@tanstack/react-query"
 import { AxiosError } from "axios"
 import { useSnackbar } from "notistack"
 import { useEffect } from "react"
-import { ParamImportance } from "ts/types/optuna"
 import { useAPIClient } from "../apiClientProvider"
 
 export const useParamImportance = ({
@@ -13,7 +13,7 @@ export const useParamImportance = ({
   const { enqueueSnackbar } = useSnackbar()
 
   const { data, isLoading, error } = useQuery<
-    ParamImportance[][],
+    Optuna.ParamImportance[][],
     AxiosError<{ reason: string }>
   >({
     queryKey: ["paramImportance", studyId, numCompletedTrials],
diff --git a/optuna_dashboard/ts/types/optuna.ts b/optuna_dashboard/ts/types/optuna.ts
index 01844f722..f69d008a6 100644
--- a/optuna_dashboard/ts/types/optuna.ts
+++ b/optuna_dashboard/ts/types/optuna.ts
@@ -21,12 +21,6 @@ export type TrialParam = {
   distribution: Optuna.Distribution
 }
 
-export type ParamImportance = {
-  name: string
-  importance: number
-  distribution: Optuna.Distribution
-}
-
 export type SearchSpaceItem = {
   name: string
   distribution: Optuna.Distribution