PURPOSE: To polish a tape always to a definite face roughness even when the hardness and the temperature in the polishing operation of an optical-disk master disk are changed.

CONSTITUTION: The polishing position of an optical-disk master disk 30 is detected by a position detection part 46. The number of revolutions of the optical-disk master disk 30 or the feed speed of a polishing tape is changed by a detection signal in a rotation part 43 according to a polishing position so that the relative speed of the polishing tape and the optical-disk master disk is made definite. In addition, light is shone at the polishing face of the optical-disk master disk 30, its reflected light is detected, a polishing pressure is changed automatically by a detection signal, and the polishing time is controlled. Thereby, an irregularity in the thickness due to the polishing operation of the optical-disk master disk can be eliminated, and a polishing speed can be increased remarkably. In addition, irrespective of the hardness and the temperature in the polishing operation of the optical-disk master disk, the tape can be polished always to a definite polishing face, and the optical-disk master disk whose reliability is high and whose accuracy and quality are always high can be manufactured.