To provide an image of a desired magnification without geometric positional information.

The image processing device comprises: an image acquisition means for acquiring a radiation image of a marker, which is formed of a substance of a large coefficient of radiation attenuation and imaged together with a subject for computing the magnification for correction; a marker detecting means for detecting the image of the marker captured in the acquired radiation image; a correction magnification computing means for computing the magnification for correction based on the result of detection of the maker by the marker detecting means and preset information on the marker; and a scale correcting means for correcting the scale of the subject in the radiation image based on the computed magnification for correction.