Provided is an electron microscope wherein a detector requiring the application of a voltage is used to obtain a micrograph from a sample placed in a gas atmosphere. The electron microscope is provided with a gas inlet device for emitting gas onto a sample, and a gas control device controlling the amount of gas emitted by the gas inlet device so that, during the gas emission by the gas inlet device, the degree of vacuum within the space where the detector (49-51, 55) is installed is continuously maintained to less than a set value.