A disc cartridge housing a disc-shaped recording medium in a main cartridge body portion is disclosed. The disc cartridge includes a main cartridge body portion having a circular medium housing section for rotationally housing a disc-shaped recording medium, a recording and/or reproducing opening for exposing at least a portion of the disc-shaped recording medium to outside and a driving opening for allowing intrusion of a rotating driving unit adapted for rotationally driving the disc-shaped recording medium. The disc cartridge also includes a shutter mechanism having a shutter member rotated along the major surface of the main cartridge body unit in a region provided with the medium housing section to open/close the recording and/or reproducing opening and a plurality of cartridge supporting portions at plural corner regions of larger area outside a region provided with the medium housing section of the main cartridge body unit. The disc cartridge is loaded on the recording and/or reproducing apparatus by the cartridge supporting portions being supported by a positioning mechanism provided on the recording and/or reproducing apparatus.