A technique of adequately determining the position of the bone resection plane of artificial joint replacement and the size of the implant. The three-dimensional relative position relation (the three-dimensional position relation between the relation among frontal three elements and the relation among lateral three elements) among the five elements, i.e., a frontal The source of X-ray (FS), the plane (PS) to which the frontal radiograph belongs, a lateral The source of X-ray (FL), the plane (PL) to which the lateral radiograph belongs, a lateral The source of X-ray (FL), the plane (PL) to which the lateral radiograph belongs, and three-dimensional CAD data is determined (S7), shade images (IU, IL) of three dimensional CAD data on the implant are superimposed in an adequate position shown in the radiograph, and the images are displayed on a display (112) (S9, S10).