A composite antenna includes a plurality of unit structures arranged in a first plane direction, a reference conductor serving as a reference potential of the plurality of unit structures, and an antenna element provided around the arranged plurality of unit structures and electromagnetically connected to the reference conductor. The plurality of unit structures each includes a first resonator extending in the first plane direction, a second resonator away from the first resonator in a first direction and extending in the first plane direction, and a connector magnetically or capacitively connecting the first resonator and the second resonator in the first direction.