Scanning electron microscope having a monochromator

A scanning electron microscope comprising:

• an electron source;
• an objective lens for focusing an electron beam emitted from the electron source on a sample;
• a monochromator that is disposed between the electron source and the objective lens and that monochromatizes energy of the electron beam,
• a first focusing lens for adjusting focusing of the electron beam entering the monochromator;
• and
• a first astigmatism correcting lens for correcting astigmatism of the electron beam entering the monochromator,
• wherein the first focusing lens and the first astigmatism correcting lens are between the electron source and the monochromator and
• wherein the scanning electron microscope further comprises an adjustment means of obtaining an image of an electron-beam adjustment sample disposed where the electron beam is focused in the monochromator, and based on the obtained image, driving the first focusing lens and the first astigmatism correcting lens so that focusing and astigmatism of the electron beam entering the monochromator are adjusted.