A charged particle beam apparatus includes a sample chamber; a sample stage; an electron beam column irradiating a sample S using an electron beam; and a focused ion beam column irradiating the sample S using a focused ion beam. The apparatus includes an electrode member displaceable between an insertion position between a beam emitting end portion of the electron beam column and the sample stage and a withdrawal position distant from the insertion position, the electrode member being provided with an electrode penetrating hole passing the electron beam therethrough. The apparatus includes a driving unit displacing the electrode member; a power source applying a negative voltage to the electrode member; and an insulation member electrically insulating the sample chamber the driving unit from the electrode member.