A disk cartridge for such as an optical disk, which increases rigidity at an opening for a recording/reproducing unit. The disk cartridge (10) comprises an upper shell (12), a center frame (14) and a lower shell (16) that are clamped and fixed, wherein the opening ends of a center frame opening (20) and a lower shell opening (22) that expose downward the recording surface of a recording medium (18) housed between the center frame (14) and the upper shell (12) are integrally linked together by a reinforcing member (24) and a lower shell reinforcing member (26) respectively.
