To facilitate assembly, and to use parts in common by forming central axes in the longitudinal direction of a first lead-out section and a second lead- out section on the central axis of a concentric circle, mutually reversing the directions of the first and second lead-out sections and constituting the first and second lead-out sections of a concentric circle symmetric to a straight line passing the central axes.

A flat wire 12 is wound in multiple turns in the thickness direction while leaving a first lead-out section 1a, and a first winding section 2a consisting of a concentric circle is formed. Winding is reversed continuously, a second winding section 2B composed of a congruent concentric circle to the first winding section 2a is formed, and a second lead-out section 1b is led out. Central axes in the longitudinal directions of the first lead-out section 1a and the second lend-out section 1b are placed on a straight line 7 tying the central axes of the first and second winding sections 2a, 2b. The directions of the first and second lead-out sections 1a and 1b are reversed mutually, and the lead-out sections 1a and 1b are composed of concentric circles symmetric to the straight line 7 passing the central axes 6a, 6b.