To remove and clean metal foreign matters, added and attracted by a bar magnet tube, with an easy structure.

When Fe-alloy foreign matters C are attracted on the periphery of the bar magnet tube 1, the bar magnet tube 1 is drawn inside a cylinder 4 by injecting pressurized air from an inlet and outlet port 9. Then, since the magnetic flux of the bar magnetic tube 1 is short-circuited by an eliminating ring 20, the magnetic flux flows to the eliminating ring 20 that is a magnetic material. Therefore, the short-circuited spacer 16 loses the magnetic flux. Fe- alloy foreign matters such as an iron powder, attracted on the periphery of the bar magnetic tube 1, moves to the front end face of the eliminating ring 20 by the magnetization of a magnetic material, and thereby, the foreign matters are removed.