A printed wiring board has a core substrate including an insulative base material and having a penetrating hole, a first conductive circuit formed on a first surface of the substrate, a second conductive circuit formed on a second surface of the substrate, and a through-hole conductor including a copper-plated film and formed in the penetrating hole such that the through-hole conductor is connecting the first and second conductive circuits. The insulative base material of the substrate includes reinforcing material and resin and has a thermal expansion coefficient in a Z direction which is set at or above a thermal expansion coefficient of the copper-plated film of the through-hole conductor and set at or below 23 ppm, and the insulative base material of the substrate has a thermal expansion coefficient in an XY direction which is set lower than the thermal expansion coefficient of the copper-plated film of the through-hole conductor.