In the initial setting of a memory card 1, the flash check data FD stored in a flash memory 2 is read out, this data FD is compared with the operation check data FD11 stored previously in the ROM, the write check data FD12 stored in the ROM 4a is written, if a fault is not detected, to the flash memory 2, and this data is read again and is compared with the write check data. FD12 of the ROM 4a. When any fault is not detected in comparison of these data, the CPU determines that the flash memory 2 is normal. Moreover, if a fault is detected in the comparison of data, the CPU sets the reset process fault data to a register 5a to set a controller 3 to the sleep mode. When the command CMD is received during this period, data comparison is executed again.