An observation device is an observation device observing an observation target and includes: an emission light source that generates emission light； a projection light source that generates projection light； a scanning mirror that scans the emission light and the projection light toward the observation target along the same optical path； a light guide optical system that guides detection target light generated in the observation target in accordance with emission of the emission light without it passing through the scanning mirror； an optical detector that detects the detection target light guided by the light guide optical system； and a control unit that controls an intensity of the projection light on the basis of a result of the detection of the detection target light.
