An inspection device (1) includes a light source (10) projecting excitation light to an inner surface of a container (20); an imager (11) capturing a fluorescence image of fluorescence emitted from a foreign substance in response to the excitation light projected; and a detector (13) detecting the foreign substance adhering to the inner surface of the container from the fluorescence image captured by the imager. The foreign substance contains a material emitting fluorescence in response to the excitation light projected to the material. The detector includes a calculator (14) calculating an average brightness value in an inspection target region, and an adjuster (15) adjusting an image-capturing condition where the fluorescence image is captured such that the average brightness value falls within a preset range.