A radiation image capturing apparatus includes an image capturing device having a tomosynthesis control mechanism for moving a radiation source and a radiation conversion panel, which are disposed on the respective opposite sides of a subject, respectively in opposite directions in synchronism with each other, a longitudinal direction moving mechanism for moving an image capturing range of the image capturing device in a longitudinal direction of the subject, an image reconstructing unit for generating a single three-dimensional image from a plurality of radiation images captured in a single image capturing range, an image joining unit for joining a plurality of three-dimensional images generated by the image reconstructing unit with respect to a plurality of image capturing ranges, in the longitudinal direction of the subject, and a projection image generating unit for generating a two-dimensional projection image on an arbitrary image plane based on a joined three-dimensional image.