A scanning electron microscope capable of performing alone the critical dimension measurement and the defect inspection is provided. The scanning electron microscope has a reference image storage unit for storing a reference image transcribing a reference pattern, an inspected image pick-up unit for picking up, on the basis of the reference image, an inspected image transcribing an inspection pattern which pattern-matches with the reference pattern, a critical dimension measuring unit for measuring critical dimensions of the inspection pattern by using the inspected image, and a defect inspection unit for performing an inspection of a defect inside or outside the inspection pattern by comparing the reference image with the inspected image.