Abstract: A charged particle beam generating apparatus of multi-stage acceleration type includes a charged particle beam source and a multi-stage acceleration tube having a plurality of acceleration electrodes arranged in cascade over a plurality of stages within the tube. A plurality of outer shield electrodes are disposed in concentrical relation on the radially outer side of the multi-stage acceleration tube over the plural stages to be applied with the same potentials as those of the associated acceleration electrodes respectively. Finally, a plurality of dividing resistors are disposed outside of the multi-stage acceleration tube or between the outer shield electrodes and the multi-stage acceleration tube so as to apply predetermined potentials to the acceleration electrodes, respectively.