A printed wiring board includes a substrate, a first conductor layer formed on first surface of the substrate, a second conductor layer formed on second surface of the substrate, a through-hole conductor penetrating through the substrate and connecting the first and second conductor layers, a build-up layer formed on the second surface of the substrate and including conductor layers and insulating layers, and a first insulating layer formed on the first surface of the substrate such that the first insulating layer is covering the first conductor layer on the substrate. The substrate has a cavity penetrating through the first insulating layer and substrate such that the cavity is exposing the build-up layer on the second surface of the substrate, and the substrate and insulating layers in the build-up layer are formed such that difference between thermal expansion coefficients of the substrate and insulating layers is set 15 ppm or less.