PURPOSE: To make a device inexpensive by combining an automatic changer and a subsystem, making a cartridge inserting hole of the automatic changer corresponding to an inserting hole of the subsystem and making effective use of the existing subsystem with the automatic changer.

CONSTITUTION: The automatic changer 1 is provided with a housing racks 2 for housing cartridges, an elevator 3 as a loading means capable of vertically moving or carrying in and out the cartridge, its power source 4, an ODD 5 and the cartridge inserting hole 6. The subsystem 7 is mounted with an ODD 8 of a magneto-optical drive, etc., having the cartridge inserting hole 9 and a built-in PSU 10 for driving a drive. The inserting holes 6 and 9 are matched in height, and are matched in their relative position by simultaneously inserting the cartridge or a gauge in an equivalent shape into the inserting holes 6 and 9. Consequently, the cartridges can be changed between the automatic changer and the subsystem (existent), and hence an inexpensive discoid recording medium library system can constituted.