An X-ray tube generates X-rays. An X-ray detector detects X-rays generated from the X-ray tube and transmitted through an object to be examined. A rotating frame continuously rotates the X-ray tube and the X-ray detector around the object. A reconstruction unit reconstructs a plurality of first volume data sets with different scan times for the same scan area of the object on the basis of an output from the X-ray detector. An image processing unit generates single second volume data set corresponding to a maximum value, an average value, a median value, or minimum value of the plurality of reconstructed first volume data sets in the temporal direction.