An artificial medium includes: a dielectric layer having a front surface and a back surface; a plurality of first grid lines respectively formed on the front surface and the back surface and extending in a first direction and a plurality of second grid lines extending in a second direction different from the first direction; and electrically conductive elements respectively formed on the front surface and the back surface of the dielectric layer and located in areas where the first grid lines intersect the second grid lines, wherein when an electromagnetic wave propagated in the direction of the thickness of the dielectric layer is incident, a current excited by the electromagnetic wave is increased in a prescribed operating frequency and a current loop is formed in a plane parallel to the direction of the thickness.