A cartridge is composed of a cartridge body and a shutter. A hologram recording disk is rotatably contained in a disk recess formed in the cartridge body. The shutter comprises upper and lower shutter plates between which the cartridge body is interposed. The shutter opens and closes openings formed in both surfaces of the cartridge body. When the shutter is kept in a closed position where the openings are closed, the edges of the shutter are inserted into slits formed around the opening. Further, a groove is formed at an end portion of the shutter. Into the groove, a ridge formed on the cartridge body is inserted.