A radiation therapy apparatus includes a manipulator a radiation head a correction unit and first and second controllers. The manipulator includes an arm movable about n axes (where n is 6 or more). The radiation head, supported by the arm, is configured to emit radiation. The correction unit continuously corrects positional coordinates of the radiation head on the manipulator so that radiation emitted from the radiation head is directed onto a reference point while the radiation head is moved along a predetermined route on a virtual sphere having the reference point as its center. The first controller controls the manipulator so that the radiation head is moved along the route using the corrected positional coordinates. The second controller causes the radiation head to emit radiation toward the reference point as the radiation head passes through radiation emission points on the route.
