A disk cartridge of the present invention comprises a case body having a disk-storage portion and an opening/closing cover having a pair of disk holding members that hold a disk in its inplane direction. A grip of the opening/closing cover engages with a grip-guide part of the case body. They may be formed asymmetrically with respect to the center line of the opening/closing cover in its insertion direction, thus preventing the opening/closing cover from being inserted into the case body upside down.