A disk cartridge comprises a cartridge housing (12) having a disk compartment (16) formed therein by overlapping a pair of shells (13), (15), an optical disk (11) rotatably stored within the disk compartment (16) and a pair of shutter members (18a), (18b) attached to the cartridge housing (12) in such a manner that they can be moved and which close and open an opening portion (25) bored through the cartridge housing (12) so that a part of the optical disk (11) can be exposed, wherein the opening portion (25) is extended in the diametrical direction of the optical disk (11) through the central portion of the lower shell (15). Two optical heads can be used simultaneously by widening the opening portion into and from which the turntable, the optical head and the like are inserted and ejected as much as possible, and efficiency with which the optical head approaches the innermost periphery of the disk-like recording medium can be improved.