A method of manufacturing a wiring substrate including the steps of, obtaining a temporary substrate from a prepreg, and concurrently attaching a
metal foil onto at least one surface of the temporary substrate, by disposing the
metal foil on a prepreg through a underlying layer interposed between them, in a way that the underlying layer is disposed in a wiring formation region on the prepreg, and the
metal foil having a size larger than that of the underlying layer is caused to contact with an outer
peripheral portion of the wiring formation region, and then by hardening the prepreg with heating and pressurization, forming a build-up wiring layer on the
metal foil, and obtaining a wiring member in which the build-up wiring layer is formed on the
metal foil, by
cutting out a portion of structure in which the underlying layer, the
metal foil and the build-up wiring layer are formed on the temporary substrate, the portion corresponding to a
peripheral portion of the underlying layer, and thus by separating the metal foil from the temporary substrate.