When a charged particle beam aperture having an annular shape is used, since a charged particle beam directly above the optical axis having the highest current density in the charged particle beam is blocked, it is difficult to dispose the charged particle beam aperture at an optimal mounting position. An charged particle beam apparatus includes a charged particle beam source that generates a charged particle beam, a charged particle beam aperture, a charged particle beam aperture power supply that applies a voltage to the charged particle beam aperture, an objective lens for focusing the charged particle beam on a sample, a detector that detects secondary charged particles emitted by irradiating the sample with the charged particle beam, a computer that forms a charged particle beam image based on the secondary charged particles detected by the detector, in which the position of the charged particle beam aperture is set so that the charged particle beam image does not move and changes concentrically in synchronization with the AC voltage, in a state where an AC voltage is applied to the charged particle beam aperture by the charged particle beam aperture power supply.