PURPOSE: To remarkably lower a friction failure of a gap by inserting plural ribbon spacers after extracting a bobbin spacer and removing them after a prepared inserting plate is attached.

CONSTITUTION: A field magnet valve 1 is connected to a frame 9, then, a center holding portion 10, a voice coil bobbin 7, and a coupling cone 11 are respectively connected to constitute prepared parts. Thereafter, a bobbin spacer 18 is covered on a center pole 3 and said bobbin 7 is inserted into an outer circumference of the spacer 18. At the same time, an outer circumference the center holding portion 10 is attached to the frame 9. Then, the spacer 18 is removed, an end of the ribbon spacer 19 is inserted between an inner circumference of the bobbin 7 and an outer circumference of the center pole 3 and the other end is inserted into a through hole 20. Then, an inserting plate 13 of a prepared inserting plate 17 and an edge outer circumference 15 respectively are fixed to a coupling cone flange portion 12 and an outer circumference of a frame 16 and thereafter, the spacer is removed.