An ion beam device according to the present invention includes a gas field ion source (1) including an emitter tip (21) supported by an emitter base mount (64), a ionization chamber (15) including an extraction electrode (24) and being configured to surround the emitter tip (21), and a gas supply tube (25). A center axis line of the extraction electrode (24) overlaps or is parallel to a center axis line (14A) of the ion irradiation light system, and a center axis line (66) passing the emitter tip (21) and the emitter base mount (64) is inclinable with respect to a center axis line of the ionization chamber (15). Accordingly, an ion beam device including a gas field ion source capable of adjusting the direction of the emitter tip is provided.