A circuit pattern 2a, made of copper foil, is arranged on a substrate 1. A nickel-containing barrier metal layer 2b is formed on the circuit pattern 2a. A gold layer 2c is formed on the barrier metal layer 2b by electroless substitution plating. Then, substrate 1 is heated up to impel nickel contained in the gold layer 2c to move toward a surface zone of the gold layer 2c to deposit nickel compound in the surface zone of the gold layer 2c, thereby enhancing the fineness of a remaining part of the gold layer 2c at at least an inside zone immediately below the surface zone. Then, the surface zone containing the crowded nickel compound is removed off the gold layer 2c so as to expose a purified surface of the inside zone of the gold layer 2c. Therefore, it becomes possible to form an excellent electrode having satisfactory bondability to the wire by using a less amount of gold at low costs.