A wiring board includes: an insulating layer; a pad including: an upper surface; a lower surface opposite to the upper surface; and a side surface between the upper surface and the lower surface, wherein the side surface and the lower surface of the pad are embedded in the insulating layer; and a metal post formed on the upper surface of the pad and including: an upper surface; a lower surface opposite to the upper surface; and a side surface between the upper surface and the lower surface, wherein a narrowed portion is formed in the side surface of the metal post.