A power transmission coil includes a plurality of coil members each of which having a length capable of surrounding at least one power reception device located under water from all directions and that are configured to wirelessly transmit power to the power reception device. Each of the plurality of coil members includes a polygonal pipe having a polygonal shape in which a plurality of straight pipes are welded, and a conductive wire that is inserted into the polygonal pipe and is wound a plurality of times.