PROBLEM TO BE SOLVED: To obtain a CT image with improved image quality. An X-ray CT apparatus 1 can orbit around a mounting portion on which an irradiated object is placed, and is irradiated by an X-ray irradiation portion that irradiates X-rays and an X-ray irradiation portion. It includes an X-ray detection unit that detects X-rays that have passed through the body, and an image reconstruction unit that reconstructs an image of a tomographic image of the irradiated body based on the X-ray image data detected by the X-ray detection unit. .. The image reconstructing unit 17 is an X-ray detector in consideration of the atomic number density and atomic number per unit volume in each of the compartments included in the plurality of three-dimensional spaces in which the irradiated body is partitioned by a predetermined size. Among the detected X-rays, the scattered radiation components scattered in each of the plurality of three-dimensional spaces are calculated, and the image is reconstructed in consideration of the scattered radiation components. [Selection diagram] Fig. 3【課題】画質が向上したＣＴ画像を得る。【解決手段】Ｘ線ＣＴ装置１は、被照射体が載置される載置部周りに周回可能であり、Ｘ線を照射するＸ線照射部と、Ｘ線照射部から照射されて被照射体を通過したＸ線を検出するＸ線検出部と、Ｘ線検出部で検出されたＸ線画像データに基づいて、被照射体の断層の画像を再構成する画像再構成部と、を備える。画像再構成部１７は、被照射体を所定の大きさで区画した複数の３次元空間に含まれる区画のそれぞれにおける単位体積当たりの原子個数密度及び原子番号を考慮して、Ｘ線検出部において検出されたＸ線のうち複数の３次元空間それぞれにおいて散乱された散乱線成分を算出し、当該散乱線成分を考慮して画像の再構成を行う。【選択図】図３
