The invention provides a disc changer including a plurality of trays which can be moved respectively in a horizontal direction, a tray driving gear unit capable of shuttling the trays between a standby position and a disc exchange position, a gear driving mechanism for driving the tray driving gear unit, a tray triggering unit capable of locking/unlocking the trays in the standby position, pushing all trays to engage with the tray driving gear unit after unlocking the trays, and driving the trays toward the disc exchange position, wherein all trays in the standby position can be unlocked and pushed to engage with the tray driving gear unit, and ejected outward from a mechanical chassis by a predetermined tray stroke, thereafter the trays are driven back to the standby position one by one, and when the last tray reaches the standby position all trays are locked.