PURPOSE: To facilitate manufacture by superposing an inner cylinder and an outer cylinder, in which cylinders in which a plurality of coil strand sheets are arranged are twisted in the clockwise direction and the counterclockwise direction, in two layers, bringing a ring, to one side thereof a plurality of conductors are fixed, into contact with the end section of the cylinder and ultrasonic-welding the ring.

CONSTITUTION: A plurality of coil stand sheets 2 are disposed in parallel, thus forming a cylinder. A slight difference is shaped between the diameters of one cylinder and the other cylinder so as to be precisely superposed, and the cylinders are twisted in the clockwise direction and the counterclockwise direction, thus forming a coil A. A large number of conductor pieces 8 are fastened on one side of an annular insulating substrate 7 having the same size as the diameter of the coil A at regular intervals, thus shaping a substrate 6 for joining. The coil A is held by a jig, and the conductor pieces 8 for the substrate 6 for joining are brought into contact with the end surface of the coil A, and ultrasonic-welded by the end section of a horn for an ultrasonic welder. Accordingly, a welding process is shortened remarkably, and the area of welding is increased, thus improving conductivity and reliability.