A wiring substrate has pads formed from a plurality of metal layers and vias connected to the pads. The plurality of metal layers have a metal layer exposed through the wiring substrate, and a first metal layer which is interposed between the metal layer and the vias and which prevents diffusion of metal included in the vias into the metal layer. A second metal layer which is less subject to oxidation than the first metal layer is provided between the vias and the first metal layer, and the vias are connected to the second metal layer.