PROBLEM TO BE SOLVED: To reduce the acquisition frequency of positional information on an object of irradiation such as imaging of a transparent image and generate a model with higher accuracy at the time of generating a model indicating the position of the object of irradiation for radiation therapy.SOLUTION: A model generation apparatus includes: a reference model storage part which stores a reference model of the movement of the object of irradiation periodically moving; a respiratory signal acquisition part which acquires a respiratory signal being a signal generated in synchronization with respiration; a position information acquisition control part which makes an irradiation object position information acquisition device which acquires information indicating the position of the object of irradiation acquire information indicating the position of the object of irradiation at a prescribed timing indicated by a phase of the respiratory signal; and a model generation part which generates an irradiation obje
