Two radiation images are acquired by emitting radiation to a subject from two imaging directions that form a first imaging angle, and two radiation images are acquired imaged from two imaging directions that form a second imaging angle. The radiation images of the first imaging angle are displayed as two-dimensional images while the radiation images of the second imaging angle are displayed as a stereoscopic image. Designation of a predetermined position in the radiation images that are displayed as two-dimensional images is received to obtain position information. The obtained position information in the radiation images of the first imaging angle is projected onto the radiation images of the second imaging angle based on the position information and three-dimensional position information is obtained. Based on the three-dimension position information, markers are displayed on the radiation images of the second imaging angle which are displayed as a stereoscopic image.
