In a radiographic apparatus according to this invention, when an imaging system scan is performed, a imaging system scanner moves an X-ray tube, which emits a cone-shaped X-ray beam, on one linear track, and an FPD, which detects transmission X-ray images of an object under inspection, on the other linear track synchronously with movement of the X-ray tube. Thus, a non-revolving type imaging system scan is carried out. When an X-ray sectional image reconstruction is performed, a sectional image reconstructing unit reconstructs X-ray sectional image from X-ray detection signals of transmission X-ray images of the object detected by the FPD at different radiographic angles. At this time, a time lag remover uses lag-free X-ray detection signals with lag-behind parts removed from the X-ray detection signals. As a result, the lag-behind parts included in the X-ray detection signals, which would cause a lowering of image quality, are removed in advance of a reconstruction of X-ray sectional images.