A wiring substrate is provided with a substrate, a conductive circuit formed on a surface of the substrate, and an insulating layer which covers the conductive circuit. In a fitting portion of the wiring substrate, the insulating layer is formed with an opening portion through which a portion of the conductive circuit is exposed or displayed as an exposed surface. On the exposed surface of the conductive circuit, an electrode layer is formed which is made of a conductive member. A bottom surface of the electrode layer is connected to the conductive circuit. An upper surface of the electrode layer is extended in the widthwise direction W of wirings of the conductive circuit so as to cover even a part of the insulating layer.