A printed wiring board includes a build-up layer including an insulating layer and a first conductor layer including a component mounting pad, a covering layer formed on the build-up layer such that the covering layer is covering the insulating layer and has opening exposing the pad, a reinforcement layer formed on the covering layer and having cavity exposing the pad and the covering layer, a conductor layer formed on the reinforcement layer such that the conductor layer is on the opposite side of the covering layer on the build-up layer, and a via conductor formed in the reinforcement layer such that the via conductor electrically connects the first conductor layer and conductor layer on the reinforcement layer. The first conductor layer is embedded in the insulating layer forming a surface of the build-up layer such that the first conductor layer has surface exposed on the surface of the build-up layer.