A resonator antenna includes a first conductor pattern as a first conductor, a second conductor pattern as a second conductor, a plurality of first openings, a plurality of interconnects, and a power feed line. The first conductor pattern has, for example, a sheet shape. The second conductor pattern has, for example, a sheet shape, and at least a portion thereof (which, however, may be nearly the entirety thereof) faces the first conductor pattern. A plurality of first openings is provided in the first conductor pattern. The interconnect is provided in each of a plurality of first openings, and one end thereof is connected to the first conductor pattern. The power feed line is connected to the first conductor pattern. Unit cells including the first opening and the interconnect are repeatedly, for example, periodically disposed.