Abstract: An observation device includes a microscope. The microscope includes an illumination light beam source, an illumination optical system, and an observation optical system forming an optical image of an observation target from reflected light beams obtained by reflection of illumination light beams by the observation target. The observation optical system includes a phase plate changing the phase of directly reflected light beams reflected on a reflection surface among the reflected light beams. Both the illumination optical system and the observation optical system are arranged under the observation target. The observation device includes an image pickup device photoelectrically converting the optical image obtained by the observation optical system to create image data of the observation target and a display device displaying the image data. The illumination light beam emitted from the illumination optical system is a collimated light beam.