A subtraction image is generated by performing subtraction between a mask image serving as a radiation image obtained by capturing an object, at least of a specific region of which does not include contrast medium, and a live image serving as a radiation image obtained by capturing the object which includes the contrast medium. The emphasis degree serving as the degree of emphasis processing for the subtraction image is determined based on at least either the mask image or live image. The emphasis processing is performed for the subtraction image based on the emphasis degree.
