Abstract: A scanning electron microscope having a unit for reducing image obstacle in an scanning electron microscope which is capable of inexpensively and readily reducing image obstacle caused by any external disturbance such as alternative magnetic field and mechanical vibration in relation to the location of installation of the microscope. In order to reduce the image obstacle, the electron beam deflectors or image shift coils for forming visual image by scanning the surface of sample by using collimated electron beam, is applied superimposing with alternative current for forming alternative magnetic field of the identical frequency, identical intensity, and inverted phase of vibration to the external disturbance to cancel out the fluctuation caused by the external disturbance in the sample surface at the focal plane of the electron beam.