The particle beam therapy system, the present invention provides a particle beam irradiation system capable of high-speed scanning of a particle beam even when the field size is large. The first deflection device the maximum deflection amount of deflection in the direction the first deflection device with a maximum deflection amount of the movement up to the maximum width of the target in one direction a particle beam (21), particle beam (1) is ( and a second deflection device less than the maximum amount of deflection 21) and (22), performs control to move the particle beam to increase the amount of deflection of the (22) the second deflector during the movement of the particle beam, a particle beam The dwell in, along with reducing the amount of deflection of the (22) second deflection device, by changing the deflection amount first deflection device (21), the position of the particle beam in the target so that the retention, and the second deflector I have to perform replacement control the deflection slide into replacing the deflection (21) a first deflector deflection (22).本発明は粒子線治療装置において、照射野サイズが大きい場合でも粒子線の高速走査ができる粒子線照射システムを提供する。粒子線を一方向に標的の最大幅まで移動可能とする最大偏向量を有する第一偏向装置(21)と、粒子線(1)を上記一方向に偏向する最大偏向量が第一偏向装置(21)の最大偏向量よりも少ない第二偏向装置(22)とを備え、粒子線の移動時には第二偏向装置(22)の偏向量を増加させて粒子線を移動させる制御を行い、粒子線の停留時には、第二偏向装置(22)の偏向量を減少させるとともに、第一偏向装置(21)の偏向量を変化させて、標的における粒子線の位置が停留するように、第二偏向装置(22)の偏向を第一偏向装置(21)の偏向に置換してゆく偏向置換制御を行うようにした。
