A printed wiring board includes: a core substrate having a core layer and first and second conductor layers; a first build-up layer including a first insulating layer, an inner first conductor layer, an outermost first insulating layer, and an outermost first conductor layer; and a second build-up layer including a second insulating layer, an inner second conductor layer, an outermost second insulating layer, and an outermost second conductor layer. Each conductor layer includes metal foil, seed layer, and electrolytic plating film, t1/T1, t2/T2, u1/U1 and u2/U2 are smaller than 1, and s1/S1 and s2/S2 are larger than 1, where t1, t2, u1, u2, s1 and s2 are electrolytic plating film thicknesses of the first and second and outermost and inner first and second conductor layers, T1, T2, U1, U2, S1 and S2 are metal foil thicknesses of the first and second and outermost and inner first and second conductor layers.