HEROKU - REACTJS Unexpected token '<'

Question

    **import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './app/app';
import reportWebVitals from './reportWebVitals';

ReactDOM.render(
  <App/>,
  document.getElementById('root')
);

reportWebVitals();**

WHEN I DEPLOY, IT SEEMS THAT MISTAKE:

file:///app/src/index.js:8
<App/>,

SyntaxError: Unexpected token '<'