Abstract: The observation device 1 is a device capable of substantially simultaneously acquiring the fluorescence image and the interference image on the common observation plane in the observation object 90 mounted on slide glass 41, and has an excitation light source 11, a filter 12, a dichroic mirror 13, a lens 14, a dichroic mirror 15, an objective lens 16, a filter 17, a fluorescence imaging unit 18, an interference imaging light source 21, a filter 22, a dichroic mirror 23, a lens 24, a half mirror 25, an objective lens 26, a lens 27, a dichroic mirror 28, an interference imaging unit 29, a position detection light source 31, a light detection unit 32, the slide glass 41, an actuator 42, a reference mirror 43, an actuator 44, a control unit 51, and a display unit 52.