To completely remove minute foreign matters stuck during the spattering by bringing the disk surface into contact with water after the formation of a protective layer and performing tape cleaning after dewatering.

The processing in which a disk formed with a protective layer is brought into contact with water is carried out by atomization, immersion, etc., while the contact time with water is set within the range of 10-300 seconds. The contact with water for ten seconds or longer can reduce the generation of scratch in the tape cleaning that follows successively. The dewatering is continued until a dry state is obtained in the appearance. The disk 1 is chucked in the center opening 1a by the chuck at the tip end of the spindle and rotated around the axial center at 2,800 rpm for example. A grinding tape 2 is fed along the plate face of this disk 1 at a prescribed speed. This grinding tape 2 to be used is the one on which grinding grains are carried such as alumina grains and SiC grains.