PURPOSE: To easily erase all the files in a short time by recording a directory containing information indicating that it is the directory for erasing the entire file in a directory part.

CONSTITUTION: For erasing a file A, by recording a directory 306 indicating the erasure of a specific file as shown in the figure, the file A, that is, data A(1) to A(3) are logically erased. For erasing all the currently effective files remaining on a card, that is, files B and C, by recording a directory 307 indicating the erasure of all the files in the directory part, the files B and C are logically erased. Thus, the erasure of all the files can be executed with simple method and only little time is required for erasing them.