An electron microscope equipped with a monochromator that has a first energy filter for dispersing an electron beam according to kinetic energy, an energy-selecting slit disposed on an energy dispersive plane, and a second energy filter for canceling energy dispersion of the electron beam passed through the energy-selecting slit, said electron microscope comprising: an image acquiring portion for obtaining an electron microscope image containing interference fringes of the electron beam formed by an aperture located behind the monochromator, characterized in that the electron microscope further comprises: a line profile acquiring portion for obtaining a plurality of line profiles passing through the center of the aperture on the electron microscope image; an energy dispersion direction identifying portion for identifying the direction of energy dispersion of the monochromator on the basis of the plurality of line profiles obtained by the line profile acquiring portion; and an optics controller for controlling an optical system on the basis of a line profile in the direction of energy dispersion to bring a focal plane for the electron beam exiting from the monochromator into coincidence with an achromatic plane, wherein said energy dispersion direction identifying portion finds the ratio of a local maximum value to a local minimum value for each of the plurality of line profiles and identifies said direction of energy dispersion on the basis of the found ratios and takes the direction of the line profile having the lowest value of contrast ratio (A/B) as the direction of energy dispersion of the monochromator, wherein said optics controller controls said optical system on the basis of the ratio of a local maximum value to a local minimum value of the line profile in said direction of energy dispersion and controls the strength of the electromagnetic field of at least one of the first energy filter and second energy filter such that the contrast ratio (A/B) of the line profile in the direction of energy dispersion maximizes. an image acquiring portion for obtaining an electron microscope image containing interference fringes of the electron beam formed by an aperture located behind the monochromator, characterized in that the electron microscope further comprises: a line profile acquiring portion for obtaining a plurality of line profiles passing through the center of the aperture on the electron microscope image; an energy dispersion direction identifying portion for identifying the direction of energy dispersion of the monochromator on the basis of the plurality of line profiles obtained by the line profile acquiring portion; and an optics controller for controlling an optical system on the basis of a line profile in the direction of energy dispersion to bring a focal plane for the electron beam exiting from the monochromator into coincidence with an achromatic plane, wherein said energy dispersion direction identifying portion finds the ratio of a local maximum value to a local minimum value for each of the plurality of line profiles and identifies said direction of energy dispersion on the basis of the found ratios and takes the direction of the line profile having the lowest value of contrast ratio (A/B) as the direction of energy dispersion of the monochromator, wherein said optics controller controls said optical system on the basis of the ratio of a local maximum value to a local minimum value of the line profile in said direction of energy dispersion and controls the strength of the electromagnetic field of at least one of the first energy filter and second energy filter such that the contrast ratio (A/B) of the line profile in the direction of energy dispersion maximizes. a line profile acquiring portion for obtaining a plurality of line profiles passing through the center of the aperture on the electron microscope image; an energy dispersion direction identifying portion for identifying the direction of energy dispersion of the monochromator on the basis of the plurality of line profiles obtained by the line profile acquiring portion; and an optics controller for controlling an optical system on the basis of a line profile in the direction of energy dispersion to bring a focal plane for the electron beam exiting from the monochromator into coincidence with an achromatic plane, wherein said energy dispersion direction identifying portion finds the ratio of a local maximum value to a local minimum value for each of the plurality of line profiles and identifies said direction of energy dispersion on the basis of the found ratios and takes the direction of the line profile having the lowest value of contrast ratio (A/B) as the direction of energy dispersion of the monochromator, wherein said optics controller controls said optical system on the basis of the ratio of a local maximum value to a local minimum value of the line profile in said direction of energy dispersion and controls the strength of the electromagnetic field of at least one of the first energy filter and second energy filter such that the contrast ratio (A/B) of the line profile in the direction of energy dispersion maximizes.