An X-ray tube 1 is heated under an X-ray scan condition (tube voltage V, tube current I, exposure time width t) and thus a focal point is shifted. Artifact occurs in a reconstructed image due to the focal point shift. The present invention has an object to enable correction of the focal point shift caused by heating the tube. The applicant and inventor of this application has confirmed that the focal point shift amount of the tube 1 varies in accordance with whether it is in a heating direction or cooling direction when viewed from a past sequence. Therefore, the sequence record and the focal point shift amount based on the heating and cooling directions are stored as data in a storage device 13. A just near past sequence record when viewed from now is stored in a storage unit 16, and the tube temperature is detected by a tube temperature detector 15. On the basis of this temperature and the data in the storage unit 16, heating or cooling and the present accumulated heat capacity are determined in a determining unit 17, and the storage device 13 is accessed to determine a focal point shift amount. The position of the tube is corrected on the basis of this shift amount.