A CT image creation apparatus for charged particle beam therapy includes: an image acquisition unit that acquires X-ray image data, which is imaged every predetermined set rotation angle, while rotating a rotating gantry to which an X-ray tube that emits X-rays and an X-ray detector that detects X-rays emitted from the X-ray tube are fixed a reconstruction unit that reconstructs a CT image on the basis of the X-ray image data a first detection unit that detects a difference between an angle of the rotating gantry, at which the X-ray image data has been imaged, and the predetermined rotation angle on the basis of the CT image and a first correction unit that corrects the X-ray image data on the basis of a detection result of the first detection unit. The reconstruction unit reconstructs the CT image on the basis of X-ray image data corrected by the first correction unit.
