Abstract: A stamper for making a read-only optical disk includes an irregular pattern for forming embossed pits based on recording information and an irregular pattern for forming dummy irregularities. The irregular pattern for the embossed pits is arranged in a region corresponding to an information area for recording information in the read-only optical disk. The irregular pattern for the dummy irregularities is arranged in a region corresponding to an area between the information area and the outer periphery of the disk.

Abstract: An automatic stamper exchange device for effecting automatic stamper exchange to and from a mold of an injection molding apparatus includes a first stamper housing unit, a second housing unit, a stamper mounting and dismounting unit and a stamper supplying unit. A used-up stamper is housed in the first stamper housing unit, and a new stamper is housed in the second housing unit. The stamper mounting and dismounting unit dismounts the new stamper from the metal mold or mounts the used-up stamper on the metal mold. The stamper supplying unit houses the used-up stamper dismounted by the stamper mounting and dismounting unit in the first stamper housing unit or takes out the new stamper housed in the second stamper housing unit to supply it to the stamper mounting and dismounting unit.