A control method of a memory device including a storage area formed of a nonvolatile semiconductor memory, includes updating a file stored in the storage area by using a file system which supports an incremental write method, recording, in the storage area, an allocation table representing a correlation between a logical address indicating a recording position of the file and a virtual address representing a virtual recording position of the file and management information of the allocation table, and recording position information representing a recording position of the management information in a position information area of the storage area.