Abstract: A printed wiring board includes a core substrate, and a buildup layer formed on the core substrate and including an interlayer resin insulation layer and a conductive layer. The core substrate includes a metal core, a first insulation layer on first surface of the metal core, a first conductive layer on the first insulation layer, a second insulation layer on second surface of the metal core, and a second conductive layer on the second insulation layer, the metal core has a penetrating hole penetrating from the first surface to the second surface and a resin portion filling the penetrating hole, the resin portion includes resin material from the first insulation layer, the core substrate has a through-hole conductor formed in the resin portion through the metal core, the interlayer resin insulation layer has a core material, and the first insulation layer does not have a core material.