The present invention is intended to enable proper elimination of the remanent magnetization of the scanning magnet, which is used in a particle beam therapy system, in a short time. In the particle beam therapy system that irradiates an irradiation target with a particle beam 18 accelerated by an accelerator and scanned by scanning magnets 11 and 12, power supplies 13 and 14 to operate the scanning magnets 11 and 12 output pattern currents for demagnetizing the scanning magnets 11 and 12. The pattern current is controlled by a control circuit 15 that reads a demagnetization pattern 17 and controls the power supplies 13 and 14.
