An X-ray CT apparatus of the present invention includes an image reconstruction unit that, according to scanning conditions, acquires an irradiated X-ray image which is the distribution of the irradiation intensity of X-rays irradiated to an object by an X-ray irradiation unit, performs projection conversion of the irradiated X-ray image and a reconstructed image, and generates an exposure dose image, which is an image showing the distribution of an exposure dose of the object, and also calculates the exposure dose using the projection-converted reconstructed image and an irradiated X-ray image corresponding to a generation region of the reconstructed image.