A wiring board includes first and second insulating layers, first and second through holes, a via, a plane layer, and signal wirings. The first insulating layer covers a first wiring layer. The first through hole opens on a surface of the first insulating layer and exposes a surface of the first wiring layer. The via fills the first through hole. The plane layer is connected to the via and is stacked on the first insulating layer. The second through hole opens on a surface of the plane layer and exposes the surface of the first insulating layer. The second insulating layer at least partially fills the second through hole and covers the plane layer. The signal wirings are stacked on the second insulating layer. The first through hole overlaps the signal wirings in a plan view. The second through hole does not overlap the signal wirings in a plan view.