PROBLEM TO BE SOLVED: To support a medical staff to promptly and appropriately make an intervention judgment for treatment such as suspension of particle beam therapy and change of conditions in a particle beam irradiation process. A proton beam treatment system 1 includes an irradiation nozzle 25 for irradiating a target 31A with a particle beam, a proton beam irradiation control device 41 for controlling the irradiation nozzle 25, and a particle beam with which the target 31A is irradiated. Dose monitor 27B for measuring the irradiation amount of, the position monitor 27A for measuring the position of the particle beam irradiated on the target 31A, and the irradiation for calculating the dose distribution of the particle beam irradiated on the target 31A during irradiation. A dose distribution evaluation system 55 is provided. [Selection diagram]【課題】 粒子線の照射過程において粒子線治療の中止,条件変更等の治療への介入判断を医療従事者が迅速、且つ適切に行うことを支援する。【解決手段】 陽子線治療システム1は、標的31Aに対して粒子線を照射するための照射ノズル25と、照射ノズル25を制御する陽子線照射制御装置41と、標的31Aに照射される粒子線の照射量を計測する線量モニタ27Bと、標的31Aに照射される粒子線の位置を計測する位置モニタ27Aと、標的31Aに対して照射される粒子線の線量分布を照射中に算出する照射中線量分布評価システム55を備えている。【選択図】 図1