An electron microscope is offered which can adjust an energy-selecting slit in a short time by smoothly moving the slit. The electron microscope (100) includes an electron beam source (10) emitting an electron beam (EB), an energy filter (22) producing a deflecting field in the path of the electron beam (EB) to disperse the beam (EB) according to energy, a slit plate (24) disposed on an energy dispersive plane and provided with at least one energy-selecting slit (25), a current measuring section (50) for measuring the electrical current of the beam (EB) absorbed into the slit plate (24), and an energy filter controller (60) for controlling the intensity of the deflecting field of the energy filter (22) on the basis of results of measurements made by the current measuring section (50).