A positioning apparatus and a positioning method has a control element and function 40 includes a radiograph acquisition element 41 that acquires radiograph data detected by two radiography systems selected from a group consisting of a flat panel detector, a DRR (Digital Reconstructed Radiograph) generation element 42 that generates DRR in two different directions by virtually performing fluoroscopic projection relative to the 3-dimensional CT data obtained through the network 17, a positioning element 43 that positions a CT to the X-ray fluoroscopic radiograph obtained from two radiography systems, and a displacement distance calculation element 44 that calculates a displacement distance of the tabletop 31 based on the gap between radiographs for improved positioning. The positioning element 43 has a multidimensional optimization element 45 and a 1-dimensional optimization element 46 that optimize parameters relative to rotation and translation of the fluoroscopic projection to maximize an evaluation function that evaluates a matching degree between the DRR and the X-ray fluoroscopic radiograph.
