PURPOSE: To provide the clean etching method.

CONSTITUTION: Metallic layers 120a, 120b are first formed in prescribed patterns on a substrate 110, the surface of which consists of diamond. Metals which can solutionize diamond (for example, metals contg. at least one among iron, cobalt and nickel, or the alloys thereof, etc.) are used for these layers. The substrate is then subjected to a heating treatment. The carbon atoms on the diamond surface are solutionized successively to the metallic layers from the boundary between the diamond on the substrate surface and the metallic layers by executing the heating. The solutionized carbon atoms diffuse into the metallic layers and precipitate on the surface on the side (vapor phase side) opposite from the metallic layers. A series of reaction including solutionization, diffusion and precipitation of the carbon atoms progress and the diamond on the substrate surface is successively etched. After the etching is executed by heating for the prescribed period of time, the metallic layers are removed by melting, etc., to complete the etching.