A disk cartridge is provided which houses an optical disk rotatably. It includes a cartridge body having formed therein a head opening through which a part of the optical disk is exposed to outside, and a shutter member supported movably on the cartridge body to uncover and cover the head opening. A first concavity is formed on a side of the cartridge body over which the shutter member slides and in a region opposite to a region where the shutter member is moved, across the head opening, a bent portion is formed along one lateral side of the shutter member to close a gap resulted between the shutter member and first concavity when the shutter member has been moved to a position to cover the head opening, and a second concavity deeper than the first concavity is formed at a part of the first concavity, adjacent to the head opening.