A radiographic apparatus according to this invention includes a back projection arithmetic processing unit which, when carrying out a back projection arithmetic process on projection data detected by a flat panel X-ray detector (FPD) 3 to reconstruct a sectional image, reconstructs the image using data R derived from an addition average according to a width L (of a range at which X rays for a thickness w arrive) determined by a point P, which is a reconstruction position, and a projection angle θ. Thus, image blurring due to the reconstruction position and projection angle θ can be reduced.
