PURPOSE: To permit polishing of the surface of a stone material only through the polishing by a grinding stone, by fixing chips which are formed by solidifying the minute powder such as diamond into the alternate circular-arc form divided, onto the undersurface of a rotary disc by a bonding agent.

CONSTITUTION: A penetration hole 2 is formed at the center of a disc 1 made of aluminum, and also an installation hole is formed on the surface. The base part 5 in the upper part of a chip 4 is formed of synthetic resin, and the lower part 6 is formed by solidifying the minute powder such as diamond by a bonding agent. Said chips 4 are arranged on the outer peripheral edge of the disc 1 and on the alternate circular-arcs which are formed by dividing an imaginary circle formed between the outer peripheral edge and a center point into a plurality of equal parts. In the above-described constitution, an installation pipe 11 is inserted into the penetration hole 2, and a rotary shaft 8 is inserted into the installation pipe 11. Therefore, when the disc 1 is revolved on the surface of a stone material 7, the water film on the surface of the stone material 7 is removed rapidly, and the chips 4 constact with the stone material 7, and an expected purpose can be achieved.