1. A radiographic apparatus having a receiving device for receiving a patient thereon, a radiation emitting device, with an irradiation field control device for emitting radiation toward the patient, a radiation detecting device for detecting radiation transmitted through the patient to carry out radiographic imaging by obtainig radiographic images based on the detected radiation, the irradiation field control device controlling and restricting an irradiation field emitted from the radiation emitting device to be narrower than an irradiation field projected to the radiation detecting device, the radiographic imaging being carried out with the radiation emitting device emitting radiation and the radiation detecting device detecting the radiation while, with the irradiation field restricted to be narrow by the irradiation field control device, the radiation emitting device and the radiation detecting device move parallel to each other in the same direction along a longitudinal direction of the patient relative to the receiving device, the apparatus comprising a center calculating device for determining a shifted center of radiographic image detected in a state of the irradiation field restricted to be narrow by the irradiation field control device, and a shift calculating device for determining a shift of the center of the radiographic image from a positional relationship between the center of the radiographic images and the irradiation field of the radiation detecting device.