To suppress the electrification of the surface while keeping the resolution to reduce the distortion of a secondary electron image by positive electrification by adding the function of modulating the scanning speed of electron or the luminance of an electron beam. to interrupt the scanning of the electron beam.

An electron beam 110 incident on a silicon wafer 111 by an electron gun 101 is scanned by a horizontal scanning electromagnetic coil 102 and a vertical scanning electromagnetic coil 103. A vertical scanning electromagnetic coil current 105 has a saw-tooth waveform, while a horizontal scanning electromagnetic coil current 104 is modulated to a step-like waveform by a horizontal scanning signal modulation device 107. Consequently, a locus 112 of the electron beam for scanning the electron beam on the surface of the silicon wafer 111 is formed of the part horizontally rested or slowly scanned and the part scanned at high speed. This repeat of scanning is set to about 11-10 Hz. Since the amplitude of scanning is changed with a constant scanning period when the observation magnification is changed, the linear speed of scanning is changed inversely proportional to the magnification.