A printed wiring board includes a resin insulating layer, a wiring conductor layer embedded in the insulating layer such that the conductor layer has a first surface exposed on a first surface side of the insulating layer, and a conductor post formed on a second surface of the conductor layer on the opposite side with respect to the first surface such that the conductor post has a side surface covered by the insulating layer. The conductor post has an end surface on the opposite with respect to the conductor layer such that the end surface of the conductor post is exposed on a second surface side of the insulating layer, and the conductor post has an end portion on a wiring conductor layer side such that the side surface in the end portion is a curved side surface which is bending outward increasingly toward from the conductor layer.