In a disk array device for cooling respective sections including a HDD by a fan, drop of cooling efficiency by the difference of conditions of HDD mounted and unmounted sections is prevented and the use of a dummy HDD is deleted / eliminated. A housing contains a HDA mounted on the HDD, a power controller board for performing control to the HDD, a power unit for supplying power to each section, a fan for cooling the housing therein, and a backboard for connecting all the sections. On one backboard surface, the HDA is mounted, which has a cooling function for making cooling air flowing in the housing and exhausting air from the housing via a region on which the HDA are mounted and via a vent hole on the backboard. For the vent hole, a shutter is mounted, which has a mechanism for adjusting an open area rate of the vent hole by opening when the HDA is mounted and closing when removed.