The present invention aims to implement a patient QA which excluded both of the static and dynamic uncertainty without a dose detector having high position resolution. A dose distribution calculating device (10) of the present invention includes: a beam information memory unit (a measured energy memory unit (14), a measured charge memory unit (12), a measured beam center axis memory unit (13)), measuring particle beam information of a particle beam (20) generated from a particle beam therapy device (50) by a measuring device during a confirmation irradiation irradiating the particle beam (20) to a phantom (21) belonged to a replacement of a treatment target, and the beam information memory unit memorizes the measured particle beam information； and a total dose calculating unit (15), calculating irradiation dose distribution (total dose distribution (Di)) according to the measured particle beam information (measured energy (E), measured beam amount (measured charge amount (Q)), and measured beam central axis position (Px, Py)).本發明之目的在於實現無須高位置解析度之線量檢測器，且可將靜態及動態的不確定性皆排除之患者QA。本發明之線量分布演算裝置(10)係包括：射束資訊記憶部(測量能量記憶部(14)、測量電荷記憶部(12)、測量射束中心軸記憶部(13))，於對屬於治療對象的代替物之假體(21)照射粒子射束(20)之確認照射中，藉由測量裝置測量粒子線治療裝置(50)所產生之粒子射束(20)的粒子射束資訊，而該射束資訊記憶部記憶該測量粒子射束資訊；以及合計線量演算部(15)，係依據測量粒子射束資訊(測量能量(E)、測量射束量(測量電荷數(Q))、測量射束中心軸位置(Px,Py))來演算照射線量分布(合計線量分布(Di))。
