A discharging part of an X-ray generator using a one-side earthed X-ray tube, i.e., the anode or cathode is earthed is identified on the basis of the tube voltage detected value and the tube current detected value. For the identification, the X-ray generator comprises a device comprising tube voltage decrease slope calculating means (S4) for calculating the slope of decrease with time of the tube voltage detected value, tube current increase calculating means (S4) for calculating the increase of the tube current detected value in a predetermined time, first judging means (S5) for judging whether or not the slope of the tube voltage decrease calculated in the tube voltage decrease slope calculating means exceeds its acceptable value, second judging means (S6) for judging whether or not the increase of the tube current calculated in the tube current increase calculating means exceeds its acceptable value, and discharge portion identifying means (S7, S8) for identifying the discharging part which is in the X-ray tube or a high-voltage generating unit on the basis of the results of the judgments made by the first and second judging means. The identified discharging part is displayed on display means (S9).Therefore, provided is a small-sized high-reliable X-ray generator having a function of identifying a discharging part with high accuracy.
