An X-ray computer tomography apparatus includes an X-ray tube, an X-ray detector, a rotating mechanism, a reconstruction unit which reconstructs multislice or volume image data based on the projection data detected by the X-ray detector, a profile generating unit which generates a CT value profile in the slice direction for each pixel by using image data, a profile portion extraction unit which extracts a profile portion exceeding a predetermined threshold from each of the CT value profiles, a scattered radiation distribution estimation unit which estimates a scattered radiation distribution centered on the profile portion based on the CT value integral and width of the profile portion, and a scattered radiation correction unit which corrects the image data based on the estimated scattered radiation distribution.
