An antenna substrate comprising: a cap substrate comprising a first insulating layer, a plurality of first antenna conductors arranged lengthwise and crosswise on both upper and lower surfaces of the first insulating layer and aligned to face each other with the first insulating layer interposed in between, and a first connection pad disposed on an outer peripheral edge of the lower surface of the first insulating layer; a frame substrate comprising a second insulating layer, a second connection pad disposed on an outer peripheral edge of an upper surface of the second insulating layer, and a third connection pad disposed on an outer peripheral edge of a lower surface of the second insulating layer; and a base substrate comprising a third insulating layer, a plurality of second antenna conductors arranged on an upper surface of the third insulating layer, and a fourth connection pad disposed on an outer peripheral edge of an upper surface of the third insulating layer, wherein the first connection pad and the second connection pad are connected to each other, the third connection pad and the fourth connection pad are connected to each other, and the base substrate, the frame substrate, and the cap substrate are layered in this order, the second insulating layer comprises a plurality of first opening portions each having an outer periphery located radially outward from an outer periphery of each of the first antenna conductors on the lower surface of the first insulating layer, respectively, in a top view, and each of the first opening portions is disposed to encircle the outer periphery of each of the first antenna conductors on the lower surface of the first insulating layer, respectively, and each of the first opening portions has a circular shape. a cap substrate comprising a first insulating layer, a plurality of first antenna conductors arranged lengthwise and crosswise on both upper and lower surfaces of the first insulating layer and aligned to face each other with the first insulating layer interposed in between, and a first connection pad disposed on an outer peripheral edge of the lower surface of the first insulating layer; a frame substrate comprising a second insulating layer, a second connection pad disposed on an outer peripheral edge of an upper surface of the second insulating layer, and a third connection pad disposed on an outer peripheral edge of a lower surface of the second insulating layer; and a base substrate comprising a third insulating layer, a plurality of second antenna conductors arranged on an upper surface of the third insulating layer, and a fourth connection pad disposed on an outer peripheral edge of an upper surface of the third insulating layer, wherein the first connection pad and the second connection pad are connected to each other, the third connection pad and the fourth connection pad are connected to each other, and the base substrate, the frame substrate, and the cap substrate are layered in this order, the second insulating layer comprises a plurality of first opening portions each having an outer periphery located radially outward from an outer periphery of each of the first antenna conductors on the lower surface of the first insulating layer, respectively, in a top view, and each of the first opening portions is disposed to encircle the outer periphery of each of the first antenna conductors on the lower surface of the first insulating layer, respectively, and each of the first opening portions has a circular shape.