A support member is designed to move in the longitudinal direction in a rack mount type disk array apparatus. A frame member is attached to the support member for relative rotation around the rotation axis located between the front and rear ends of the frame member in the longitudinal direction. Recording disk drives are held within the frame member in an upright attitude. The recording disk drives can be removed from and inserted into the frame member in a facilitated manner. This leads to a facilitated replacement of the recording disk drives. Moreover, the upper face of the frame member is allowed to face forward through the rotation around the rotation axis. Even if the disk array apparatus is placed at a higher level, the operator easily accesses the recording disk drives in the frame member.