PROBLEM TO BE SOLVED: To provide a treatment planning device and a radiation treatment system in which the number of times of executing optimization calculation and dose calculation having high calculation cost can be reduced, and thereby the efficiency of making a treatment plan can be improved.SOLUTION: A treatment planning device includes: an input device 102 for inputting an irradiation angle and an irradiation weight of each gate determined by an operator; a data server 107 for storing multiple treatment plan data; an arithmetic processing unit 105 for making DVH statistical information every irradiation angle by using irradiation angle information and dose distribution information every irradiation angle contained in multiple treatment plan data stored in the data server 107, and calculating predictive DVH in the whole gate irradiation by using the dosage histogram every each gate calculated based on the DVH statistical information and the irradiation angle information and the irradiation weight of each gate being input with the input device 102; and a display device 103 for displaying the predictive DVH calculated by the arithmetic processing unit 105.SELECTED DRAWING: Figure 1COPYRIGHT: (C)2020,JPO&INPIT【課題】計算コストの高い最適化計算・線量計算を実施する回数を削減でき、治療計画の作成の効率を向上させることが可能な治療計画装置および放射線治療システムを提供する。【解決手段】操作者が定めた各門の照射角度および照射ウエイトを入力する入力装置102と、複数の治療計画データを記憶するデータサーバ107と、データサーバ107に記憶された複数の治療計画データに含まれる照射角度情報および照射角度毎の線量分布情報を用いて照射角度毎にDVH統計情報を作成し、DVH統計情報と入力装置102で入力された各門の照射角度情報および照射ウエイトに基づいて算出した各門毎の線量ヒストグラムを用いて、全門照射での予測DVHを算出する演算処理装置105と、演算処理装置105によって算出された予測DVHを表示する表示装置103と、を備えている。【選択図】図1