A method of a pre-treatment process for coating notably improves both the surface roughness of a coating layer of a cemented carbide cutting tool and the bonding force of the coating layer to the substrate. According to the method, a sintered surface layer within a range of 0.5-5 μm, which corresponds to the tungsten carbide particle size of a substrate, is properly removed from the substrate surface of a cemented carbide cutting tool. Thus, a porous sintered surface layer having a non-uniform structure is removed and a substrate surface having high structure density and evenness is provided compared to blasting pre-treatment. In order to obtain a sufficient bonding force between a coating layer and the substrate, the surface ratio of open pores, which exist around tungsten carbide particles appearing by removal of the porous sintered surface, is equal to or more than 5%.