A wiring substrate includes a core substrate including a glass substrate and a through-hole conductor formed in the glass substrate, a resin insulating layer formed on the core substrate and including resin and inorganic particles, a conductor layer formed on the insulating layer and including a seed layer and an electrolytic plating layer, and a via conductor formed in the insulating layer such that the via conductor is electrically connected to the through-hole conductor formed in the glass substrate and includes the seed layer and electrolytic plating layer extending from the conductor layer. The conductor layer and the via conductor are formed such that the seed layer is formed by sputtering, and the resin insulating layer has an opening in which the via conductor is formed such that the inorganic particles include first particles forming an inner wall surface in the opening and second particles embedded in the insulating layer.