The present invention provides a charged particle beam device which can effectively restrain misalignment of an optical axis even if a position of an anode is changed. The present invention is a charged particle beam device comprising a cathode provided with a charged particle source which emits a charged particle, an anode which applies an electric field to the emitted charged particle, a charged particle beam deflector which deflects an orbit of a charged particle beam having passed the anode, and a charged particle beam detector which detects the charged particle beam from a sample to which the charged particle is irradiated, wherein a distance changing mechanism which changes a distance between the cathode and the anode, corresponding to a charged particle amount emitted from the charged particle source and a deflection amount control mechanism which detects a condition of the deflector under which the charged particle dose detected from the sample scanned by deflecting the charged particle beam in the changed distance becomes a desired size and controls deflection of the deflector at sample measurement on the basis of the condition are provided.