A disk cartridge, which is easy to handle, is provided. The disk cartridge includes a cartridge main body having: an opening facing a disk; and a shutter for opening and closing the opening. A part of the cartridge main body is formed in an approximately semicircular shape. Such a shape allows a user to easily know an insertion direction. Moreover, since the cartridge main body does not have any corners, the insertion into a drive device is simplified. The shutter is provided pivotably for the cartridge main body. Any one of a plurality of types of medium can be provided in the disk cartridge. When the disk cartridge is inserted into an external device such as the drive device, the device receives a signal indicating the type of medium, which is transmitted through an electric terminal, so as to perform a process in accordance with the type of medium.