1. A radiographic apparatus having a radiation emitting device for emitting radiation toward a patient, and a radiation detecting device for detecting radiation transmitted through the patient, to carry out radiation image pickup by obtaining radiographic images based on the detected radiation, the radiation emitting device and the radiation detecting device being constructed movable parallel relative to each other in the same direction along a longitudinal direction of the patient, the radiation emitting device emitting radiation and the radiation detecting device detecting radiation transmitted through the patient irradiated while the radiation emitting device and the radiation detecting device move every predetermined distance relative to the patient, said apparatus comprising a correcting device for correcting radiographic images based on overlapping areas of a plurality of radiographic images based on the radiation detected whenever a relative movement is made in the same direction along a longitudinal direction of the patient, an image decomposing device for decomposing corrected radiographic images for the every predetermined distance, an image composing device for composing the decomposed images for each of the same projection angles to obtain a projection image for each projection angle, and a reconstruction processing device for carrying out a reconstruction process based on the composed projection images to obtain a sectional image.