According to one embodiment an antenna apparatus includes: a first conductor layer; a second conductor layer; a dielectric layer between the first and the second conductor layers; a plurality of first conductor vias corresponding to a first direction; a plurality of second conductor vias opposed to the first conductor vias corresponding to the first direction; and a plurality of first openings in the first direction in a region of the first conductor layer between the first and the second conductor vias. A plurality of third conductor vias are part of the plurality of first conductor vias and are arranged along the first openings. Positions of the third conductor vias in a second direction are different from positions of others of the first conductor vias in the second direction, the second direction is substantially orthogonal to the first direction and is substantially parallel to the first conductor layer.