[Objective] Shifts due to movement of subjects are enabled to be detected in addition to shifts at the boundaries of images due to mechanical errors when combining a plurality of radiation images obtained by lengthwise imaging. [Constitution] A mechanical error correcting section (34) corrects image distortion within images obtained by imaging due to mechanical errors in an imaging surface. A shift detecting section (35) detects amounts of shift based on body movement of a subject N within mechanical error corrected images, in which image distortion due to mechanical errors in an imaging surface have been corrected. A body movement obtaining section (36) detects the amounts of body movement during imaging based on the amounts of shift, and a body movement correcting section (37) corrects for the amounts of shift of the subject within the mechanical error corrected images, based on the amounts of body movement.
