<p>An antenna device (100) is provided with a metal cavity (10), and an antenna (20) positioned inside the metal cavity (10). Part of the metal cavity (10) is provided with an insulator or dielectric slot (11). The antenna (20) is positioned in a location where the slot (11) is excited. The gap direction of the slot (11) is orthogonal to the plane of the main polarization of the antenna (20). Consequently, the slot (11) is excited by the antenna (20), and acts as a slot antenna. An antenna device that can be provided in a metal cavity provided with a shield case and a shield function is thus configured.</p>
