A positioning apparatus automatically performs a patient positioning calculation at high speed and a positioning method. A positioning apparatus 40 has, as functional components, a DRR image generation element 41 that generates the DRR image based on the CT image data, an optimization element 43 that calculates the positional gap of the patient 57 by optimizing the fluoroscopic projection parameters； and an initial parameter adjustment element 42 that changes the initial position of the fluoroscopic projection parameters prior to optimization of fluoroscopic projection parameters with regard to the rotatable and translation of the CT image data relative to the optimization element 43.
