The invention provides an electron source including a columnar chip of a hexaboride single crystal, a metal pipe that holds the columnar chip of the hexaboride single crystal, and a filament connected to the metal pipe at a central portion. The columnar chip of the hexaboride single crystal is formed into a cone shape at a portion closer to a tip than a portion held in the metal pipe, and a tip end portion having the cone shape has a (310) crystal face. Schottky electrons are emitted from the (310) crystal face. According to the invention, it is possible to provide a novel electron source having monochromaticity, long-term stability of an emitter current, and high current density.