Illegal. It is clearly stipulated in the Labor Contract Law that the company cannot detain the employee's deposit for any reason and must return it in full. If losses are caused to employees, compensation should also be made.

So if you don't want to pay the money, you can sue, but maybe you lost your job, too.

On the other hand, you give money, but you have to keep the evidence. When you want to leave, you can use this evidence to sue the company and get it back.