An optical disk memory apparatus comprising, at least, a disk rotating mechanism (240) which drives and rotates an optical disk (140) set in the memory, an optical head (210) which projects a light beam on the optical disk and which detects reflected light from the optical disk, and head displacement means (300) including an actuator (310) for displacing the optical head. The disk rotating mechanism (240), the optical head (210) and the head displacement means (310) are arranged along a common plane. In addition, the actuator (310) is arranged at the rear of the optical head (210) with respect to a rotating shaft (241) of the disk rotating mechanism (240). Since the disk rotating mechanism (240), the optical head (210) and the head displacement means (310) are arranged in this order, the memory apparatus can be made structurally thinner. Further, it can be implemented in a card type structure.