PURPOSE: To obtain a diamond electric discharge member extremely excellent in adhesion by applying etching treatment to the surface of a sintered hard alloy, etc., allowing cluster diamond to adhere to the surface, and then forming a thin diamond film by a CVD method, etc.

CONSTITUTION: Etching treatment is applied, by acid treatment or electrolytic treatment, to the surface of a formed body composed of a sintered hard alloy, such as WC-Co, a cermet consisting of hard metal carbide, etc., and sintering auxiliary, such as Co, or a ceramics, e.g. of Si3N4, sialon, or Al2O3 type. After cluster diamond of ≤5nm average grain size is allowed to adhere by means of spray coating, etc., a thin diamond film is formed on the above surface by a vapor-phase process, etc. By this method, a cutting tool, a sliding member, etc., having diamond coating of ultra-high hardness and excellent in wear resistance can be produced.