1. A microscope image processing device for processing an observation image used for performing an observation by using a fluorescence microscope, comprising: an optical element switching unit for switchably arranging an arbitrary optical element on an optical path of fluorescence from among a plurality of types of the optical elements that transmit an excitation beam for exciting a sample and fluorescence emitted from the sample; an image pick up unit for picking up the observation image via the optical element arranged by the optical element switching unit; and an optical element determination unit for determining a type of the optical element arranged by the optical element switching unit on the basis of the observation image picked up by the image pick up unit.