A disk cartridge device includes first and second disk cartridges of different sizes for housing therein disks of different disk diameters and a cassette compartment onto which the first and second disk cartridges are selectively loaded, the cassette compartment including a pair of positioning pins having height-deciding bases for properly placing the first disk cartridge and a pair of positioning pins having height-deciding bases for properly placing the second disk cartridge, wherein the first disk cartridge has stepped escape holes formed on its lower surface to enable itself to escape from the positioning pins by which the second disk cartridge is properly positioned in the loading state when positioning holes of the first disk cartridge are properly fitted into positioning pins and the height is properly decided.