A first image obtaining unit obtains a plurality of projection images corresponding to different radiation source positions, the projection images being imaged under a first imaging condition for tomosynthesis imaging, and a second image obtaining unit obtains a two-dimensional image imaged with a given radiation source position under a second imaging condition for simple imaging. An image quality correction unit performs image quality correction on the projection images to compensate for a difference of image quality between the projection images and the two-dimensional image based on a difference between the first imaging condition and the second imaging condition. A reconstruction unit reconstructs the projection images having been subjected to the image quality correction and the two-dimensional image to generate a tomographic image of a slice plane of the subject.