A scanning electron microscope according to the present invention includes: an electron source that produces an electron beam; a trajectory dispersion unit that disperses the trajectory of an electron beam of electrons with a different energy value; a selection slit plate having a selection slit that selects the energy range of the dispersed electron beam; and a transmittance monitoring unit that monitors the transmittance of an electron beam, which is being transmitted through the selection slit. Accordingly, there can be provided a scanning electron microscope equipped with an energy filter that implements a stable reduction in energy distribution.