A transport mechanism for an optical disc cartridge capable of discharging an optical disc cartridge to a predetermined position by making a transport roller in pressure contact with the optical disc cartridge even if the cartridge is erroneously inserted. A transport roller (5) is supported by an arm (4). When the transport roller (5) is made in pressure contact with the side wall of an optical disc cartridge, the cartridge is transported. A guide arm (12) is rotatively mounted which projects into an optical disc cartridge transport path between the transport roller (5) and a disc insertion port. If the optical disc cartridge is inserted in a normal orientation, the guide arm (12) is rotated by the optical disc cartridge to rotate the arm (4) in the clockwise direction to allow the optical disc cartridge to be inserted, whereas if the optical disc cartridge is inserted in an orientation rotated by 90° from the normal orientation, the transport roller is made in pressure contact with the side wall of the optical disc cartridge.