An antenna substrate according to the present disclosure includes a first insulation layer including a first surface, a second surface located opposite the first surface, and a first through-hole conductor extending from the first surface to the second surface, a ground conductor located at the first surface, the ground conductor including a slot, a second insulation layer including a second through-hole conductor connected to the first through-hole conductor, the second insulation layer covering the ground conductor located at the first surface, and a first antenna conductor located at a surface located on the opposite side to the other surface of the second insulation layer, the other surface covering the ground conductor.