PROBLEM TO BE SOLVED: To enable detection of a luminaire failure such as disconnection of a light guiding member, without upsizing of a device.SOLUTION: An observation device 1 includes: an image acquisition part 3 that repeatedly acquires an observation object image composed of a plurality of pixels, by taking the image of an observation object part OE a failure determination area setting part 5 that sets a failure determination area for use in determination of a failure in a luminaire 2 within the observation object image a central value extraction part 6 that extracts a central value indicating a state of a pixel value in the failure determination area and a failure determination part 7 that performs the determination of the failure in the luminaire on the basis of change of the central value.
