a plurality of X-ray tubes;

a plurality of slit mechanisms which are respectively provided for said plurality of X-ray tubes and whose slit widths are adapted to be changed;

a plurality of X-ray detectors which form pairs with said plurality of X-ray tubes, each said X-ray detector including a plurality of detection elements arrayed in a matrix form in a channel direction and a slice direction;

a support mechanism which supports the X-ray tubes and the X-ray detectors so as to allow the X-ray tubes and the X-ray detectors to rotate about a rotation axis parallel to the slice direction;

a correction unit which corrects projection data from each detection element located in an area which X-rays passing through the slit mechanism directly strike, based on data simultaneously collected from at least one detection element located outside the area and associated with the same channel in order to reduce a scattered radiation component originating from X-rays generated by an X-ray tube other than the X-ray tube forming the pair; and

a reconstruction unit which reconstructs image data on the basis of the corrected data.