A wiring board adapted for mounting an electronic component has the form of a structure in which a plurality of wiring layers are stacked one on top of another with an insulating layer interposed therebetween and are interconnected through via holes formed in the insulating layers, respectively. A plurality of openings are formed through the structure in a region where a wiring is not formed, extending through the structure in a thickness direction thereof. Further, solder resist layers are formed on the outermost wiring layers, respectively, and exposing pad portions defined in desired locations in the outermost wiring layers.