已經安裝過babel和presets-es2015

package.json中都有相應依賴

{
  "name": "test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-preset-es2015": "^6.24.1",
    "gulp": "^3.9.1",
    "gulp-babel": "^6.1.2"
  }
}

gulpfile.js

var gulp = require("gulp");
var babel = require("gulp-babel");

gulp.task("es5", function() {
    return gulp.src("es5/test.js")
        .pipe(babel({
            presets: ["es2015"]               
        }))
        .pipe(gulp.dest("es6"));
});

目錄結構：

運行起來就報錯：Error: Couldn't find preset "es2015" relative to directory "C:\Users\Li\Desktop"

用：presets: ['es2015'].map(require.resolve)報：Error: Cannot find module 'es2015'

但我都安裝了呀，package.json裡面也都有顯示