Electron Gun and Electron Beam Device

An electron gun includes an emitter, an electron gun electrode, and a short-circuiting mechanism for setting the emitter and the electron gun electrode at the same potential. The short-circuiting mechanism includes a first switch member provided with a first switch electrode that is connected to the emitter and a second switch electrode that is connected to the electron gun electrode, a second switch member provided with a third switch electrode, and a drive unit that operates at least one of the first switch member and the second switch member to switch between a state in which the first switch electrode and the second switch electrode are in contact with the third switch electrode and a state in which the first switch electrode and the second switch electrode are separated from the third switch electrode. The short-circuiting mechanism has the same potential as a predetermined voltage.