Patent ID: 8263943

Claim:
An ion beam device comprising: a gas field ion source for generating an ion beam; an objective lens for focusing an ion beam extracted from the gas field ion source on a sample; a movable beam limiting aperture which limits an open angle of the ion beam to the objective lens; a sample stage on which the sample is mounted; and a vacuum vessel which houses the gas field ion source, the objective lens, the beam limiting aperture, the sample stage, and the like, wherein the gas field ion source includes an emitter tip for generating an ion, an emitter base mount which supports the emitter tip, an ionization chamber having an extraction electrode provided so as to be opposed to the emitter tip and constructed so as to surround the emitter tip, and a gas supply pipe for supplying gas to vicinity of the emitter tip, and a mechanism which produces a noncontact interaction between the emitter base mount and the vacuum vessel is provided so as to suppress fluctuations in positional relation of the emitter base mount with respect to the vacuum vessel.