Since disks of the same type are loaded in a disk device using a conventional disk changer scheme, the disk device is not versatile as a peripheral device of a computer. ROM disks and RAM disks are mixed and stored in a magazine, and this magazine is loaded in the disk device. In the disk device, a tray is identified in step (c) by a detector arranged on the tray to check whether the tray be a ROM disk or a RAM disk. Thereafter, discrimination information is recorded, together with the contents information, on an IC memory Ml arranged on the magazine in step (k), or the discrimination information are recorded, together with the identification code of the magazine, on a memory 5 in step (p). Thereafter, when the magazine is loaded again, the discrimination information is read from the IC memory M1 or the memory 5, and an operation corresponding to each disk is performed.