An antenna device 1 has a dielectric substrate 2, a patch antenna 5 and electric power absorbing passive elements 21, 24 formed on a surface of the dielectric substrate. Each electric power absorbing passive element 21, 24 is formed between the patch antenna 5 and an edge portion in a polarized wave direction of the dielectric substrate 2. The electric power absorbing passive elements 21, 24 absorb a part of electric power received by the patch antenna 5. This makes it possible to suppress a surface current flowing to the edge portions of the dielectric substrate on a conductive plate (a front-surface conductor plate 3 or a back surface conductor plate 4) on the dielectric substrate.