<p>An antenna device comprises an antenna element (101) and a non-powered element (401) that are provided on a first surface of a dielectric substrate (21), and an antenna element (501) and a non-powered element (201) that are provided on a second surface of the dielectric substrate (21). The non-powered elements (401, 501) are provided at respective positions that are separated from the antenna elements (101, 201) by 1/4 of the operating wavelength ? at the time of communication.</p>
