PURPOSE: To stabilize rotation of a disk by providing a preventing means between a cartridge holder and a cartridge to be inserted thereto so as to prevent the cartridge from inclining from the horizontal direction when the cartridge is led in by a cartridge loading-in member.

CONSTITUTION: A preventing means 98 is provided between the cartridge holder 32 and a cartridge 101 to be inserted thereto so as to prevent the cartridge 101 from inclining from the horizontal direction when the cartridge 101 is drawn by a cartridge drawing member 45. Therefore, the cartridge 101 inserted to a specified position to the cartridge holder 32 is stably led in without inclination from the horizontal direction while the cartridge is led in by the cartridge loading-in member 45 accompanied with descent of the cartridge holder 32. Then, the positioning hole 104 is surely engaged with the positioning pin 44 to accurately hold the cartridge at the specified position so that the aperture part surely faces to the pick up device and head device. Thereby, rotation of the disk can be stabilized.