An information recording medium cartridge with a disc, a cartridge casing having the disc accommodated therein, and a shutter slidably mounted to the cartridge casing. The shutter has a first shutter plate for opening and closing a recording and/or reproducing opening of the cartridge casing and a second shutter plate for opening and closing the recording and/or reproducing opening on another side. The first and second shutter plates are independently movable between first and second positions for closing and opening the recording and/or reproducing openings.