A coil is formed by coaxially winding a second winding so as to be in intimate contact with an outer circumferential portion of a first winding wound about a winding shaft axis. In the first winding, one side of a winding wire is wound from an inner circumferential side to an outer circumferential side, the other side of the winding wire is drawn forth from the inner circumferential side to the outer circumferential side, while crossing the one side of the winding wire, and a thickness in a direction of the winding shaft axis in crossing portions of the one side of the winding wire and the other side of the winding wire is equal to a thickness in other portions.