To provide a disc changer capable of working without any malfunctions in spite of a reduced number of switches, it includes a mode-detecting mechanism having means for identifying an operation, cams respectively operated by powers supplied from a first and second motors, each cam provided with said identifying means, sensors for detecting said identifying means moving according to the operation of said cam, each composed of a set of a light-emitting element and a light-receiving element, a control section for receiving operation signals detected by said sensors to control the operation of the disc changer, and transmission gears for driving said cams, said transmission gears interlocking with a transporting gear meshing with a rack of said main tray for carrying the main tray out with the subtray put thereon.