https://www.npmjs.com/package.

 1%", "last 2 versions", "not ie <= 8"]
  }
}],
"stage-2"

],
"plugins": ["transform-vue-jsx", "transform-runtime",

["component", {
  "libraryName": "mint-ui",
  "style":true
}],
["import",
  {
    "libraryName": "element-ui",
    "styleLibraryName": "theme-chalk"
  }
]

]
}
change it to one, and install another npm install babel-plugin-import-- save-dev.
there is another solution:
"plugins": [

["component",
[{
"libraryName": "mint-ui",
"style": true
},
{
"libraryName": "element-ui",
"styleLibraryName": "theme-chalk"
}]

]