Charged Particle Beam Source and Charged Particle Beam System

Provided is a charged particle beam source having an emitter that can be replaced easily. The charged particle beam source includes an electron gun chamber; a first unit including both a supportive insulative member mechanically supporting a cable and a first set of terminals electrically connected to the cable; and a second unit including both the emitter that releases charged particles and a second set of terminals electrically connected to the emitter. The chamber has a side wall provided with a through-hole in which the first unit is secured. The second unit can be detachably mounted to the first unit. Within the chamber, the emitter is placed on an optical axis, so that the first and second sets of terminals are brought into contact with each other.