An image acquisition unit acquires a plurality of projected images from a CT apparatus. A reconstruction unit reconstructs the plurality of projected images to produce a plurality of tomographic images. A scattered ray removal unit removes scattered ray components included in radiation transmitted through the subject from the plurality of projected images based on the tomographic images. The repetition unit performs repetition processing of repeating production of a new tomographic image obtained by reconstructing the projected images from which the scattered ray components are removed, and the removal of the scattered ray components from the plurality of projected images based on the new tomographic image.
