Aftastende omgevings-elektronenmicroscoop

PROBLEM TO BE SOLVED: To prevent an excessive scattering of primary electrons and deterioration in the vacuum of an electron gun chamber by providing a gas kind setting part. SOLUTION: A gas kind setting part 30 is provided, and when a gas kind which an operator uses is input thereto, the part 30 transmits an upper limit value of gas pressure to a gas pressure control part 20 while an upper limit value of secondary electron detector voltage to a secondary electron detector control part 18, these values being preliminarily stored as data in the part 30, and it is prevented that a gas pressure over these values is applied and an impressed voltage to the secondary electron detector is made. Accordingly, discharge between the secondary electron detector and a sample is prevented from generating, thereby generating no surface destruction of the sample 12 caused by the discharge and providing a proper contrast sample image.