PURPOSE: To enhance the treatment capacity to power consumption, by concentrically arranging two or more of moving magnetic field generators each of which is formed by applying winding to the inner peripheral surface of a cylindrical or arch shaped iron core in the centripetal side so as to respectively hold treatment containers between said magnetic field generators.

CONSTITUTION: Operation pieces 3 are moved in treatment containers within a magnetic field to perform each treatment of an article to be treated. The moving magnetic field generators 9A, 9B corresponding to the treatment containers 1A, 1B are respectively positioned so as to be opposed to the outer peripheral sides of the treatment containers and, by this arrangement, the iron core of the inner peripheral side moving magnetic field generator 9B is also used as the yoke heel piece be coming to a magnetic return passage opposed to the outer peripheral side moving magnetic field generator 9A. Therefore, the magnetic fluxes of the moving magnetic fields acting on the treatment containers 1A, 1B are generated from the moving magnetic field generators 9A, 9B toward the center of a cylinder, that is, the centripetal side and the magnetic flux intersecting an acting space passes to a converging direction in each treatment container.