To provide a charged particle beam exposure system capable of coping even when it becomes necessary to change the size and the form of a region on a mask which is to be irradiated at a time with a charge particle beam.

An electron beam EB generated from an electron gun 1 is shaped in a rectangular beam by a first aperture 50. The position where a second aperture 51 is irradiated with the beam shaped in a rectangle is set by using a deflector 52. Thereby the size and the form of the electron beam EB with which the mask 2 is irradiated can be arbitrarily continuously changed and set.