Disclosed is a scanning electron microscope provided with a calculation device (403) for measuring the dimension of a pattern on a sample (413), characterized in that the amount of change of a pattern shape, caused by electron beam irradiation, is calculated and stored, and a pattern shape contour (614; 815; 1512) before the sample is irradiated with an electron beam is restored from a pattern shape contour (613; 814; 1511) in a scanning electron microscope image (612; 813; 1510) after the sample is irradiated with an electron beam using the calculated amount and, then, the pattern shape contour (614; 815; 1512) is displayed. Thus, the shrinking of a resist and/or the effect of electrostatic charge caused when a sample is irradiated with an electron beam are eliminated, so that the shape contour of a two-dimensional pattern before irradiating an electron beam can be restored with a high degree of accuracy, and the dimension of a pattern can be measured with a high degree of accuracy, using the restored image.