A wiring substrate includes: a substrate having a first surface and a second surface; a first insulating layer stacked on the first surface; a pad electrode stacked on the first insulating layer; a through electrode connected to the pad electrode; and a second insulating layer disposed between the substrate and the through electrode and between the first insulating layer and the through electrode, wherein a diameter of the through electrode in a connection section between the pad electrode and the through electrode is smaller than a diameter of the through electrode on the second surface side, the first insulating layer, the second insulating layer and the through electrode overlap with each other in a peripheral area of the connection section, when seen from a plan view, and the thickness of the first insulating layer in the area is thinner than the thickness of the first insulating layer in other areas.