Two or more-staged masks are prepared for a charged beam generating source. One mask has first aperture sections having rectangular apertures arranged into a lattice form, and electrodes which deflects a beam at respective first aperture sections. The other mask has a second aperture section having basic figure apertures for shaping the beam which passes or passed through the first aperture sections. Layout data of a semiconductor apparatus are divided into sizes of the basic figures which take reduction in exposure into consideration so as to be classified according to the basic figures. The beam which is shaped into a form of an overlapped portion of the divided layouts and the classified basic figure is emitted onto a sample.