PURPOSE: To control the current value of an electron beam which is removed by providing a linear electrode at the cylindrical hollow section of an anode in parallel to the central axis and altering the potential difference between this electrode and the first electrode within an approximately zero range.

CONSTITUTION: In a crossed-field discharge type cool cathode electron generator, a linear electrode is arranged at the cylindrical hollow section 1a of an anode 1 in parallel to the central axis. When the first and second cathodes 2 and 3 are kept equipotential and the potential of an electrode 10 is finely and continuously altered within a proper positive range in which the potential difference between the cathode 2 and electrode 10 is almost equal to zero, the cathode current is continuously altered from zero to the maximum. Besides, by assigning the potential of the anode 3 lower than that of the electrode 2 without altering the electrode 10 in this state and altering either of the potential, the current applied to the cathode 2 is altered sharply. As a result, the current value of the electron beam which is removed from the opening 2a of the cathode 2 can be controlled and a stable discharge state be maintained.