A wiring substrate includes an insulating layer including inorganic fillers and resin, and a conductor layer formed on a surface of the insulating layer and having a conductor pattern. The surface of the insulating layer has an arithmetic average roughness Ra in the range of 0.05 μm to 0.5 μm, the conductor layer includes a metal film formed on the surface of the insulating layer, and the inorganic fillers include a first inorganic filler including particles such that each of the particles has a portion of a surface separated from the resin and forming a gap with respect to the resin of the insulating layer and that the metal film of the conductor layer includes part formed in the gap between the first inorganic filler and the resin.