A semiconductor device (1) is provided which includes a regular cell array unit (30), a redundant cell array unit (31) that is provided in relation to the regular cell array unit (30), and a PGM/ER state machine (20) that controls reprogramming in which, when programming of a sector in the regular cell array unit fails (step S3), data involved in the programming that fails and data already stored in the sector in the regular cell array unit are written (step S8) into the redundant cell array unit (31). Since reprogramming is performed to write the data already written in the sector as well as the data involved in the programming that fails into the redundant cell array unit (31), data loss can be prevented and data can be secured, thereby increasing the reliability of the system.