A method of detecting a wire break in a high voltage generating device that is configured to detect a wire breakage in a low-voltage cable is disclosed. The method of a wire break includes: detecting whether a wire break has occurred in each of the lines in accordance with a combination pattern of whether the time differential value of an IM signal value of a CW circuit obtained when an operating voltage is boosted is positive, negative, or 0, and whether the time differential value of a VM signal value obtained after the operating voltage is boosted by the CW circuit is positive, negative, or 0; and identifying which of the lines is broken.