A printed wiring board includes an insulating layer, a first conductor layer embedded into first surface of the insulating layer and including multiple wirings such that the wirings include connecting portions positioned to connect an electronic component, respectively, a second conductor layer projecting from second surface of the insulating layer on the opposite side, a solder resist layer formed on the first surface of the insulating layer such that the solder resist layer is covering the first conductor layer and has an opening structure exposing the connecting portions of the wirings, and multiple metal posts formed on the connecting portions respectively such that each of the metal posts has a width which is larger than a width of a respective one of the wirings having the connecting portions. The wirings are formed such that the connecting portions are positioned side by side on every other adjacent one of the wirings.