A radiation tomography method for reconstructing three-dimensional X-ray image data of a subject from a plurality of X-ray images of the subject, each of the plurality of X-ray images corresponding to a respective one of a plurality of first and second imaging angles, the plurality of the first and second imaging angles being obtained by evenly dividing an imaging angle range, the method comprising: calculating a plurality of first and second gantry angles at which a rotating traveling gantry is arranged when a first radiation source supported by the rotating traveling gantry is arranged at the first imaging angles or a second radiation source supported by the rotating traveling gantry is arranged at the second imaging angles; calculating a plurality of first and second imaging timings when the rotating traveling gantry is arranged at the respective ones of the plurality of the first and second gantry angles, from an angular velocity of the rotating traveling gantry and a measured gantry angle at a certain timing, measuring a plurality of first absolute angles at which said first radiation source is arranged when said rotating traveling gantry is arranged at the respective first gantry angles; measuring a plurality of second absolute angles at which said second radiation source is arranged when said rotating traveling gantry is arranged at the respective second gantry angles; calculating a plurality of first and second radiating timings obtained by shifting the first and second imaging timings by first and second imaging timing correction amounts corresponding to the respective first and second gantry angles and created on the basis of the respective first and second absolute angles, so as to image a plurality of X-ray images with the radiation irradiated at the first and second radiating timings from the respective on of the first and second radiation sources, the first and second imaging timing correction amounts being adapted to correct for deflections of the gantry at the respective first and second gantry angles; and calculating, on the basis of the plurality of X-ray images, three-dimensional X-ray image data of the subject. calculating a plurality of first and second gantry angles at which a rotating traveling gantry is arranged when a first radiation source supported by the rotating traveling gantry is arranged at the first imaging angles or a second radiation source supported by the rotating traveling gantry is arranged at the second imaging angles; calculating a plurality of first and second imaging timings when the rotating traveling gantry is arranged at the respective ones of the plurality of the first and second gantry angles, from an angular velocity of the rotating traveling gantry and a measured gantry angle at a certain timing, measuring a plurality of first absolute angles at which said first radiation source is arranged when said rotating traveling gantry is arranged at the respective first gantry angles; measuring a plurality of second absolute angles at which said second radiation source is arranged when said rotating traveling gantry is arranged at the respective second gantry angles; calculating a plurality of first and second radiating timings obtained by shifting the first and second imaging timings by first and second imaging timing correction amounts corresponding to the respective first and second gantry angles and created on the basis of the respective first and second absolute angles, so as to image a plurality of X-ray images with the radiation irradiated at the first and second radiating timings from the respective on of the first and second radiation sources, the first and second imaging timing correction amounts being adapted to correct for deflections of the gantry at the respective first and second gantry angles; and calculating, on the basis of the plurality of X-ray images, three-dimensional X-ray image data of the subject.