An object of the invention is to provide a charged particle beam device capable of specifying an irradiation position of light on a sample when there is no mechanism for forming an image of backscattered electrons. The charged particle beam device according to the invention determines whether an irradiation position of a primary charged particle beam and an irradiation position of light match based on a difference between a first observation image acquired when the sample is irradiated with only the primary charged particle beam and a second observation image acquired when sample is irradiated with the light in addition to the primary charged particle beam. It is determined whether the irradiation position of the primary charged particle beam and the irradiation position of the light match using the first observation image and a measurement result by a light amount measuring device.