Provided is a particle beam irradiating device, which controls a scanning device such that irradiation of particle beam on all irradiating positions of an irradiated object is repeatedly performed by a rescan number-of-times, so that the number-of-times for each irradiating position of the irradiated object irradiated by the particle beam is achieved to the rescan number-of-times. The particle beam irradiating device includes: a calculating part, to which one of a rescan number-of-times n and an irradiating intensity J that is the dose per unit time of the particle beam is inputted, to calculate the maximum value of the other one that meets the following condition P1 with respect to the all irradiating positions.J * ti <= di/n. (Condition P1)一種粒子線照射裝置,係以反覆進行對於照射對象的全照射位置照射粒子線之照射達到再掃描次數的方式控制掃描裝置,以使粒子線照射於照射對象的各個照射位置之次數達到再掃描次數,該粒子線照射裝置包括:演算部,係輸入再掃描次數n或屬於粒子線的每單位時間之線量之射束強度J之任一方,而求出針對於全部的照射位置滿足下述條件P1之另一方的值中最大之值,並對使用者進行提示。J*ti<=di/n (條件P1)1‧‧‧粒子線產生裝置2‧‧‧掃描裝置3‧‧‧線量監視器4‧‧‧記憶部5‧‧‧控制部6‧‧‧演算部7‧‧‧輸入輸出部10‧‧‧粒子線11‧‧‧照射對象21‧‧‧Y方向掃描電磁鐵22‧‧‧X方向掃描電磁鐵A‧‧‧照射位置B‧‧‧照射位置C‧‧‧照射位置
