PURPOSE: To form diamond crystals having the specific crystal interval, step, and tip shape and precisely grind a hard and fragile material such as glass by forming a polycrystalline diamond film oriented with the (100) plane on a substrate by the vapor phase synthesis method, then dry-etching it.

CONSTITUTION: Diamond crystals 1 etched with the (100) orientation plane, an intermediate layer 2, and a filling layer 4 are arranged on a substrate 3 to constitute a grinding wheel, for example. A polycrystalline diamond film oriented with the (100) plane is first formed on the substrate 3 by the vapor phase synthesis method, then diamond crystals 1 having the diamond crystal interval of 10μm or above, the step of 10μm or above, and a uniform tip are formed by dry etching. The filling layer 4 is formed in the void removed by etching so that the step becomes 10μm or above. The intermediate layer 2 made of Si, Al, and others is formed on the substrate 3 in advance before the polycrystalline diamond film 1 is formed.