An electron beam generator for multiple columns includes: a plurality of
cathodes, to which a single acceleration voltage supply applies a
negative acceleration voltage, and which thus generates thermoelectrons;
a grid for each of the plurality of cathodes, the grid converging the
thermoelectrons emitted to form a beam of electrons; a grid voltage
supply for giving the grid a potential which is negative relative to a
potential of the cathode; and a control circuit for each cathode, for
controlling the potential of the grid. The control circuit includes a
current direction restricting element connected between a positive
electrode of the grid voltage supply and the cathode, and a grid current
supplied from the grid voltage supply is caused to flow to the cathode
through the current direction restricting element.