A plane coil which reduces an increase of an effective resistance in a high-frequency area and is made thinner is provided. The plane coil is equipped with plural conductive wires which are parallel to each other, wherein the conductive wires are arranged in a plane and spirally wound, and coil ends of the respective conductive wires are electrically connected to each other at coil lead-out portions and thus are connected in parallel. The conductive wires are arranged in plane, so that a coil thickness does not increase, and the coil is made thinner. Moreover, the plural conductive wires are connected in parallel, an increase of an effective resistance due to an influence of a skin effect in a high-frequency area is reduced.