A method of treating the surface of copper is provided to ensure adhesive strength between the surface of copper and an insulating layer without forming irregularities exceeding 1 .mu.m on the surface of copper and to improve insulation reliability between wirings. A copper whose surface is treated by the above surface treating method is also provided. The method of treating the surface of copper comprises the surface of copper comprising the steps of: forming a metal nobler than copper discretely on the surface of copper; and subsequently oxidizing the surface of copper by using an alkaline solution containing an oxidant.