In the case of inspecting samples having different sizes by means of a semiconductor inspecting apparatus, a primary electron beam bends since distribution is disturbed on an equipotential surface at the vicinity of the sample at the time of inspecting vicinities of the sample, and what is called a positional shift is generated. A potential correcting electrode is arranged outside the sample and at a position lower than the sample lower surface, and a potential lower than that of the sample is applied. Furthermore, a voltage to be applied to the potential correcting electrode is controlled corresponding to a distance between the inspecting position and a sample outer end, sample thickness and irradiation conditions of the primary electron beam.