A method of detecting deficiency of an aperture used in a charged-particle-beam exposure process employing at least two exposure columns is disclosed, where each of the two exposure columns passes a charged-particle beam through the aperture formed through a mask to shape a cross section of the charged-particle beam before exposing the charged-particle beam onto an object. The method includes the steps of mounting masks having the same aperture to the at least two exposure columns; scanning, in each of the at least two exposure columns, the charged-particle beam over an area containing a mark on a surface substantially at the same height as the object after passing the charged-particle beam through the same aperture; obtaining, in each of the at least two exposure columns, a signal waveform corresponding to the scan by detecting charged particles scattered by the mark; and comparing the signal waveform between the at least two exposure columns.