In a motor including a chucking device for detachably holding a disk, the chucking device has a center case to which a central opening of the disk is inserted; resilient members received within the center case; and claw members for holding the disk in place. Each of the claw members has a tip end portion, a disk holding surface positioned axially below the tip end portion for holding the disk in place, and a recessed sliding portion formed substantially at a circumferential center region of the disk holding surface, the sliding portion serving to guide movement of the claw member. Rest portions are formed in the center case in a facing relationship with the respective sliding portions, the rest portions serving to support the respective sliding portions by contacting therewith. Each of the rest portions has an upwardly convex curved surface with which the corresponding sliding portion makes contact.