Not illegal. According to the law, the employer shall conclude a written labor contract within one month from the date of employment. It is not illegal for a supermarket not to sign the resignation manager. You can leave your job 3 days before the probation period, and 30 days before the expiration of the probation period. The supermarket has no right to refuse your resignation request. If you have submitted a resignation application for one month, you can resign directly and ask the other party to pay the salary.