The purpose of the present invention is to provide a charged particle beam device which adjusts brightness and contrast or adjusts focus and the like appropriately in a short time even if there are few detected signals. Proposed as an aspect for achieving this purpose is a charged particle beam device provided with: a detector for detecting charged particles obtained on the basis of irradiation of a specimen with a charged particle beam emitted from a charged particle source; and a control unit for processing a signal obtained on the basis of the output of the detector, wherein the control unit performs statistical processing on gray level values in a predetermined region of an image generated on the basis of the output of the detector, and executes signal processing for correcting a difference between a statistical value obtained by the statistical processing and reference data relating to the gray level values of the image.