Abstract: An X-ray apparatus comprising a step-down transformer for stepping down a line voltage, a first timer for generating a pulse signal of the pulse width corresponding to a preheating period in response to a start signal, and a second timer for generating a pulse signal of the pulse width corresponding to an X-ray radiation period in response to the stoppage of the output of the pulse signal of the first timer. The stepped down line voltage is impressed on an X-ray generator during the period of time, i.e., the preheating period for generating the pulse signal of the first timer to preheat an X-ray tube. The line voltage is impressed on the X-ray generator during the period of time for generating a pulse signal from the second timer to supply a rated tube voltage and filament voltage to the X-ray tube. At this time the X-ray tube radiates an X-ray.