In a wiring substrate according to the present invention, a base wiring board is constructed by stacking a plurality of unit wiring boards each having wiring patterns which enable an electrical connection between upper and lower sides, in a state that the plurality of unit wiring boards are connected to each other via a connection terminal, and a silicon interposer is stacked on the base wiring board via a connection terminal, and a resin portion is filled in a gap between the plurality of unit wiring boards as well as a gap between the base wiring board and the silicon interposer, and a resin portion serves as a substrate which integrates the base wiring board and the silicon interposer.