A disk array device connected to a higher-level device, including: a battery mounting unit which mounts a nickel hydrogen battery, charges a part of electric power supplied to said logic mounting unit and said memory device mounting unit, and supplies said charged electric power to said logic mounting unit and said memory device mounting unit at the time of a power failure, wherein said logic mounting unit mounts a cache memory which temporarily stores data transferred from said high-level device and performs control to write the data stored in said cache memory to said plurality of memory devices at the time of power failure, and the power supply from said batter mounting unit to said plurality of memory devices is sequentially stopped in the order of the memory device to which data writing from said cache memory has been completed at the time of the power failure.