A disk cartridge for such as an optical disk, wherein a disk brake mechanism, for fixing the optical disk when not in use and freeing it when in use, can ensure the sufficient resilient force of a disc brake spring even in a small mounting space. The disk cartridge (10) comprises a disc−shaped recording medium (18) housed between an upper shell (12) and a center frame (14), a disk brake mechanism (48) is provided with a clamping plate (50) mounted on the recording medium (18) and a brake disc (52) loosely fitted to the clamping plate (50) so as to be movable in a thickness direction thereof, and the brake disc (52) is urged toward the recording medium (18) by a disc brake spring (54) consisting of an almost conical coil spring.
