An object of the invention is to provide a charged particle beam device capable of increasing the contrast of an observation image of a sample as much as possible in accordance with light absorption characteristics that change for each optical parameter. The charged particle beam device according to the invention changes an optical parameter such as a polarization plane of light emitted to the sample, and generates the observation image having a contrast corresponding to the changed optical parameter. An optical parameter that maximizes a light absorption coefficient of the sample is specified according to a feature amount of a shape pattern of the sample (refer to FIG. 5).