An object of the present invention is to provide a scanning electron microscope including decelerating-electric-field forming means for decreasing the energy of a beam of electrons reaching a sample, and being capable of selectively detecting BSEs with high efficiency. To this end, the scanning electron microscope including the decelerating-electric-field forming means has a detector for detecting electrons. The detector includes a part for receiving the electrons at a position which is positioned outside trajectories of SEs accelerated by the decelerating-electric-field forming means, and which is further away from the optical axis of the beam of electrons than the trajectories of the SEs.