A method for manufacturing a printed wiring board including forming a penetrating hole in a core substrate, forming a first conductor on a first surface of the substrate, forming a second conductor on a second surface of the substrate, and filling a conductive material in the hole such that a through-hole conductor is formed in the hole and the first and second conductors are connected via the through-hole conductor. The forming of the hole includes forming a first opening in the first surface, forming a second opening from the bottom of the first opening toward the second surface such that the second opening has a smaller diameter than the first opening, forming a third opening in the second surface, and forming a fourth opening from the bottom of the third opening toward the first surface such that the fourth opening has a smaller diameter than the third opening.