A printed wiring board includes a laminate, conductor posts formed on a surface of the laminate, and a mold resin layer formed on the surface of the laminate such that the posts are in the mold layer covering side surfaces of the posts. The laminate includes conductor layers and one or more resin insulating layers, the conductor layers includes a first conductor layer embedded in a resin insulating layer forming the surface of the laminate and has one surface exposed on the surface of the laminate, the first conductor layer includes first and second conductor pads such that the second pads are formed on outer peripheral side of the first pads, the mold layer has a cavity exposing the first pads, the posts are formed on the second pads on the surface of the laminate, and the first conductor layer includes fan-out wirings extending from inside to outside the cavity.