Abstract: Disclosed is a method for exposing an electron beam of a beam-shaping type, wherein the electron beam can be shaped into polygon having desired size by passing through a first and a second apertures. The position of the first or the second aperture tends to be deviated from its design position due to heat, resulting in a deviation of the electron beam. According to the invention, the offset value of the real image formed on the second aperture, with respect to the ideal image, is automatically determined by detecting a current passing through the second aperture. During an electron-beam exposure for patterning, the amount of deflection of the electron beam is corrected by taking the previously obtained offset value into consideration.