PROBLEM TO BE SOLVED: To provide a low vacuum scanning electron microscope wherein secondary electrons can be efficiently detected even at a low degree of vacuum. SOLUTION: A negative voltage is applied to a sample 25 from a sample power supply 36, and the secondary electrons that have been ejected from the sample 25 are made to be accelerated in a sufficient electric field to ionize peripheral gas molecules made by the negative voltage that has been applied to the sample 25 or a periphery of the sample, and ionize the gas molecules on the periphery of the sample by colliding with them. More ions and electrons are generated by more collisions of these ionized gas molecules with the peripheral gas molecules, resulting in an electron avalanche phenomenon. Positive ions that have approached the sample 25 change into molecules from the ions after receiving electrons from the sample 25 or the periphery of the sample. By this, a sample-absorbed current can be obtained wherein the secondary electrons or the like first generated have been amplified.
