A recording medium changer comprising: a plurality of slots for storing recording mediums; a drive for performing operation using a recording medium; a conveying mechanism comprising a recording medium delivery mechanism for conveying the recording mediums between the plurality of slots and the drive, the recording medium delivery mechanism being arranged to perform the process of removing a recording medium from a slot and mount it into the drive;and a conveying mechanism control portion for controlling the operation of the conveying mechanism; characterised in that: the conveying mechanism further comprises an extendable and retractable rail portion movably supporting the recording medium delivery mechanism, wherein when the rail portion is in the retracted position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a base area slot and when the rail portion is in the extended position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a slot expansion area, and wherein the conveying mechanism control portion determining whether the slot to be accessed by the recording medium delivery mechanism is provided in said expansion area provided in an extending direction of the rail portion and based on a result of the determination is arranged to perform extension and retraction operation of the rail portion. a plurality of slots for storing recording mediums; a drive for performing operation using a recording medium; a conveying mechanism comprising a recording medium delivery mechanism for conveying the recording mediums between the plurality of slots and the drive, the recording medium delivery mechanism being arranged to perform the process of removing a recording medium from a slot and mount it into the drive;and a conveying mechanism control portion for controlling the operation of the conveying mechanism; characterised in that: the conveying mechanism further comprises an extendable and retractable rail portion movably supporting the recording medium delivery mechanism, wherein when the rail portion is in the retracted position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a base area slot and when the rail portion is in the extended position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a slot expansion area, and wherein the conveying mechanism control portion determining whether the slot to be accessed by the recording medium delivery mechanism is provided in said expansion area provided in an extending direction of the rail portion and based on a result of the determination is arranged to perform extension and retraction operation of the rail portion. the conveying mechanism further comprises an extendable and retractable rail portion movably supporting the recording medium delivery mechanism, wherein when the rail portion is in the retracted position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a base area slot and when the rail portion is in the extended position the recording medium delivery mechanism is adapted to move on the rail portion to deliver a recording medium to the slots of a slot expansion area, and wherein the conveying mechanism control portion determining whether the slot to be accessed by the recording medium delivery mechanism is provided in said expansion area provided in an extending direction of the rail portion and based on a result of the determination is arranged to perform extension and retraction operation of the rail portion.