A printed wiring board includes: a core substrate having a core layer, conductor layers on the core layer, and through-hole conductors; a first build-up layer including an insulating layer on the substrate, an inner side conductor layer on the insulating layer, an outermost insulating layer on the inner side conductor layer, and an outermost conductor layer on the outermost insulating layer; and a second build-up layer including an insulating layer on the substrate, an inner side conductor layer on the insulating layer, an outermost insulating layer on the inner side conductor layer, and an outermost conductor layer on the outermost insulating layer. Each of the conductor layers, inner side conductor layers, and outermost conductor layers has a metal foil, a seed layer and an electrolytic plating film, and that each inner side conductor layer has the smallest thickness among the conductor layers, inner side conductor layers and outermost conductor layers.