To work a material into a minute shape of stable accuracy and shorten the working time by forming a cutting edge face having shapes matching respective shapes of a plurality of minute grooves around the circumferential face of a rotary grinding wheel.

A grinding wheel part 190 is provided with an electroless nickel plating layer 190a having thickness approximately 50μm in the internal circumferential side and a grinding wheel layer 190b in the outer circumferential side. A cutting edge face 190c formed in the grinding wheel layer is composed of a plurality of projecting parts. A projecting part on the cutting edge face 190c has a shape matching the shape of a groove 1aa formed in a form. die 1. Use of this grinding wheel 19 enables the simultaneous formation of several hundreds of grooves 1aa in the form b' l, allows the respective grooves 1aa to be formed stably at a prescribed dimension accuracy, and shorten the working time.