PURPOSE: To lengthen a life of a discharge switch, to enhance economy as compared with prior art and to improve stability of a quality by forming the switch of a plurality of semiconductor switches connected in multistages.
CONSTITUTION: A discharge switch 8 is formed of a semiconductor switch group, an irregularity in switching times, an aging change are eliminated, and a life- stability are high. A power source 12 for controlling semiconductor switches 81-8N is common for the switches 81-8N, and control voltages to be supplied to the switches 81-8N are uniform. A reactor 14 is regulated to regulate a voltage value. Thus, a life-stability can be improved. Though a plurality of semiconductor switches are used, only one control power source is sufficient. Since a magnetic core insulates the control power source from the switch side, a pulse generator having a compact structure and high reliability can be obtained.