An X-ray tube and an X-ray detector are arranged opposing one another. X-rays are irradiated from the X-ray tube by revolving around the subject. An X-ray image is obtained based on the X-rays that penetrate the subject and are detected by the X-ray detector. The high voltage generator has an inverter that supplies a voltage to the X-ray tube by switching to a predetermined operating frequency during revolution of the X-ray tube. Regarding the frequency adjustable part, the operating frequency of the inverter is adjustable such that it is a multiple of the collection rate, which is the number of X-ray images obtained per one revolution of the X-ray tube. The timing generator may adjust the voltage supplied to the X-ray tube at a timing synchronized with the operating frequency of the inverter.