A disk auto-changer comprises a disk cartridge comprising a plurality of trays for supporting disks, an elevator arranged in the disk cartridge on one side thereof, and a loading mechanism for drawing the trays into the elevator from the disk cartridge and for returning them from the elevator to the disk cartridge. The loading mechanism comprises a tray engaging portion engaged with the hook portion of the tray, a belt for moving the tray engaging portion in the tray access direction, and a belt drive mechanism for driving the belt. The above structure allows an improvement in efficiency of an installation space of the loading mechanism of the disk auto-changer.