A printed wiring board includes a plurality of conductor plates that includes at least one conductor plate that is used as a lead for electrical connection with an external circuit, the conductor plates being separated spatially from one another; an insulating layer formed on or across the conductor plates or both on and across the conductor plates; and a plurality of wiring patterns formed on the insulating layer. At least one of the conductor plates is electrically connected with at least one of the wiring patterns through a via-hole.