The purpose of the present invention is to provide a scanning electron microscope that achieves an increase in both resolution and pattern recognition capability. In order to achieve the purpose, the present invention proposes a scanning electron microscope provided with a monochromator that makes an electron beam monochromatic, the monochromator including a magnetic field generator that deflects the electron beam, and an energy selection aperture that passes a part of the electron beam deflected by the magnetic field generator. An aperture that passes some of electrons emitted from the sample and a detector that detects the electrons that have passed through the aperture are disposed on a trajectory to which the electrons emitted from the sample are deflected by a magnetic field generated by the magnetic field generator.