A disk array device including a logic mounting unit which mounts a cache memory which temporarily stores data transferred from a high-level device and performs control to write the data stored in the cache memory to a plurality of memory devices at the time of power failure. The power supply from the battery mounting unit to the plurality of memory devices is sequentially stopped in an order of memory device to which data writing from the cache memory has been completed at a time of the power failure, and even after the power supply to the hard disks in which the destage has been completed is stopped, the power supply into the cache memory from the battery is continued.