PURPOSE: To convergently make a high density magnetic field function for an affected part by providing one or more bar-shaped magnetic substances respectively having sufficiently small diameters for the diameter of a cylindrical body for the inner side space position of a coil between the frange plates of a spool and positioning the tips of the respective magnetic substances on the plate surfaces of the frange plates.

CONSTITUTION: A magnetic field generator 6 has a structure in which a coil 10 is wound around the outer circumference of a synthetic resin spool 9 having a hollow hole 8 in its internal part, and the outer circumference of this coil 10 is coated with an insulating sheet, etc., according to necessity. The spool 9 is equipped with rectangular plate shaped frange plates 12 and 13 at both edges of a cylindrical body 11, plural through holes 14 and 14 are provided for the respective frange plates 12 and 13 and the cylindrical body 11 in their longitudinal directions, and magnetic bars 15 composed of silicon steel are press-fitted in the internal parts of the respective through holes 14. These magnetic bars 15 are used for converging magnetic flux generated by supplying power to the coil 10, the tips of the respective magnetic bars 15 are formed into protruding curved surfaces and positioned on the plate surfaces of the frange plates 12 and 13, and the converged magnetic flux is made to function from the top part to the external part.