An X-ray detector (320), configured to have X-ray detecting elements (322) arranged in array, detects the intensity of X-rays that are radiated from the X-ray tube (311) and have passed through a subject (500). A data processing device (420) executes steps of arranging scan data, which is based on the intensity of X-rays, in an array sequence of the X-ray detecting elements (322) or in a time sequence, to detect an anomalous scan data; associating a weight greater than “1” with scan data adjacent to the anomalous scan data, and associating a weight of “1” with other imaging data; calculating an update amount of a pixel vector that reflects these weights; and performing an iterative operation using the update amount to generate an X-ray CT image of the subject (500).