In a scanning electron microscope, a reflection plate at ground potential is provided in a specimen chamber and backscattering electrons given off from a specimen impinge on the reflection plate to generate subsidiary electrons. An electric field supply electrode applied with a positive voltage of +100 to +500V is arranged in a gap defined by the reflection plate and a specimen stage. A first detection electrode is arranged to detect ion current attributable to backscattering electrons and a second detection electrode is arranged to detect current representative of coexistence of ion currents attributable to secondary electron and backscattering electron. The scanning electron microscope constructed as above can achieve simultaneous separation/detection of secondary electron and backscattering electron.