A wiring substrate includes a first insulating layer, a conductor layer including first and second conductor pads, a second insulating layer having an opening exposing the second conductor pads, and a wiring structure including a resin insulating layer and a wiring layer and formed in the opening of the second insulating layer. The wiring structure has first surface side connection pads, second surface side connection pads and electrically connected to the second conductor pads of the conductor layer, and conductors that electrically connect the first surface side connection pads and the second surface side connection pads, the first surface side connection pads form a component mounting surface having first and second component mounting region, and the first surface side connection pads include a group of pads in the first region and a group of pads in the second region electrically connected to the group of pads in the first region.