A disc cartridge includes upper and lower shells making up a cartridge body, and with the lower shell, a first-rectangular plate, and disc holders making up the side wall of the cartridge body provided to first-side edges of the first-rectangular plate, and also slidably supporting a disc are provided, and second-side edges which face each other are opened, with the upper shell, a second-rectangular plate, standing wall members provided to third-side edges of the second-rectangular plate, making up the front and rear faces of the cartridge body, and a dividing wall provided to fourth-side edges are provided, and with the disc holders, an disc insertion/ejection opening from the second-side edges is provided to one edge, and a push-out opening for a disc push-out member is provided to the other edge, and when the shells are combined together, the second-side edges are closed, and are opened when the shells are separated.