The present invention provides an electron source that can produce a stable electron beam even if an apparatus employing the electron source receives vibration from the outside. An electron source comprising an insulator, a pair of conductive terminals attached to the insulator, a filament tensed between the pair of conductive terminals, a rod-shaped cathode having a sharp end portion performing as an electron emitting portion and joined with the filament, wherein the cathode has another end portion different from the electron emitting portion, fixed to the insulator. It is preferred that said another end portion of the cathode other than the electron emitting portion, is fixed to the insulator via a metal pin brazed with the insulator.