A charged particle beam apparatus includes a charged particle source, a separator, a charged particle beam irradiation switch, and a control device. The separator is inserted into a charged particle optical system and deflects a traveling direction of a charged particle beam out of an optical axis of the charged particle optical system or deflects the traveling direction in the optical axis of the charged particle optical system. The charged particle beam irradiation switch absorbs the charged particle beam deflected out of the optical axis of the charged particle optical system or reflects the charged particle beam toward the separator. The control device controls a charged particle beam irradiation switch.