In a particle beam therapy apparatus 100, a deflecting electromagnet 55 deflects an ion beam, and at the same time adjusts the magnetic intensity from a first magnetic field intensity higher than a target magnetic field intensity by main coils 2a and 2b to a second magnetic field intensity lower than the first magnetic field intensity and higher than the target magnetic field intensity by a predetermined amount, and thereafter compensates it to the target magnetic field intensity by compensation coils 3a and 3b that share magnetic cores 1a and 1b with the main coils 2a and 2b respectively. Thereby, the magnetic field of the deflecting electromagnet 55 is changed on the same hysteresis curve as in the case that the same energy is repeatedly delivered even if the beam energy is switched during the irradiation, and the same beam state as that at the adjustment can be realized even after the beam energy is changed.粒子線治療裝置100之偏向電磁鐵55係使離子射束偏向,並且藉由主線圈2a、2b將磁場強度從比作為目標之磁場強度更高之第一磁場強度,調整成比前述第一磁場強度更低且比前述作為目標之磁場強度高出預定量之第二磁場強度後,藉由與主線圈2a、2b分別共用磁極鐵芯1a、1b之修正線圈3a、3b修正成作為目標之磁場強度,藉此即便是在照射中切換射束能量之情形時,亦可在與反覆輸送相同能量之情形相同之磁滯曲線上使偏向電磁鐵55的磁場變化,而在變更射束能量後亦實現與調整時相同之射束狀態。
