In order to provide a stable hexaboride single-crystal field emission electron source capable of heat-flashing, this field emission electron source is provided with a metal filament, a metal tube joined thereto, a hexaboride tip that emits electrons, and graphite sheets that are independent of the metal tube and the hexaboride tip. The hexaboride tip is arranged so as not to be in structural contact with the metal tube due to the graphite sheets. The hexaboride tip, the graphite sheets, and the metal tube are configured so as to be mechanically and electrically in contact with one another.