The objective of the present invention is to provide a charged particle beam device, wherein the positional relationship between reflected electron detection elements and a sample and the vacuum state of the sample surroundings are evaluated to select automatically a reflected electron detection element appropriate for acquiring an intended image. In this charged particle beam device, all the reflected electron detection elements are selected when the degree of vacuum inside the sample chamber is high and the sample is distant from the reflected electron detectors, while a reflected electron detection element appropriate for acquiring a compositional image or a height map image is selected when the degree of vacuum inside the sample chamber is high and the sample is close to the reflected electron detectors. When the degree of vacuum inside the sample chamber is low, all the reflected electron detection elements are selected.