An oxide film formed on the surface of copper film of an electrode pad is cleaned by oxalic acid after unevenness is formed on the surface of copper film by treating the surface with organic acid. Thereby, stable resistance is obtained when carrying out a characteristic inspection by bringing a probe into contact with the electrode pad, and it is easily recognized by observation through a microscope that the probe is brought into contact with the electrode pad. In addition, wettability with respect to solder is satisfactory, and it is possible to favorably form a solder bump on the electrode pad.