Scanning electron microscope

A scanning microscope is provided for producing a scan image at high spatial resolution and in a low acceleration voltage area. An acceleration tube 9 is located in an electron beam path of an objective lens 8 for applying a post-acceleration voltage 10 of the primary electron beam. The application of an overlapping voltage 13 onto a sample 12 allows a retarding electric field against the primary electron beam to be formed between the acceleration tube 9 and the sample 12. The secondary electrons generated from the sample 12 and the secondary signals 23 such as reflected electrons are extracted into the acceleration tube 9 through the effect of an electric field (retarding electric field) immediately before the sample. The signals are detected by secondary signal detectors 24 to 27 located upwardly than the acceleration tube 9.