DISK CARTRIDGE

PROBLEM TO BE SOLVED: To move the disk information held by a disk cartridge with the disk by enabling to remove the disk from a disk cartridge main body with a disk holder and providing the information held by the cartridge on the disk holder section. SOLUTION: While a disk 4 is mounted on a disk cartridge main body 1b, sensing areas 14a, 14b, 14c and 14d, which are provided on a disk holder 5, are exposed to the external of the disk cartridge through a notch section 7 provided on the body 1b. A recording/reproducing device reads the information of the areas 14a, 14b, 14c and 14d and beforehand detects the information of the disk 4. Thus, even though the disk 4 is moved among different cartridges, the disk information held by the body 1b is also moved.