An auto-loading system for recording medium cartridges is provided which permits the simple and reliable operation of rotating the recording medium cartridges between a magazine and a drive. The auto-loading system has a cartridge tray of an elevator which is moved upward and downward between a cartridge port of the drive and a cartridge insertion port and a cartridge ejection port of the magazine within an autoloader body so that a plurality of recording medium cartridges are rotated between the magazine and the drive by the operation of ejecting the recording medium cartridges into the cartridge tray from the cartridge ejection port of the magazine by a first cartridge ejecting mechanism and the operation of ejecting the recording medium cartridges into the cartridge port of the drive or the cartridge insertion port of the magazine from the cartridge tray by a second cartridge ejecting mechanism.