In order to improve the probability of extracting a region comprising a large number of fluorescent substances, in accordance with the type of fluorescence reagent, individual differences and differences in the affected area, the present invention provides a fluorescence observation device (1) equipped with: an irradiation unit (3) for irradiating excitation light and illumination light onto a subject (F) a fluorescence imaging unit (18) for capturing fluorescence generated in the subject (F) due to irradiation of the excitation light and acquiring a fluorescence image a return-light imaging unit (19) for capturing return light returning from the subject (F) due to irradiation of the illumination light and acquiring a return-light image an extraction unit (23) for determining, from the fluorescence image, a region having a gradation value exceeding a gradation threshold value to be a region of interest and extracting this region a display unit (7) for associating and displaying the region of interest extracted by the extraction unit (23) and the return-light image a confirmation input unit (8) for allowing an observer to input confirmation as to whether the determination with respect to the region of interest displayed by the display unit (7) is correct and a threshold updating unit (26) for updating the gradation threshold value so as to reflect the input result input by means of the confirmation input unit (8).La présente invention a pour but daméliorer la probabilité dextraction dune région comprenant un grand nombre de substances fluorescentes, en accord avec le type de réactif fluorescent, des différences individuelles et des différences dans la surface affectée. A cet effet, linvention concerne un dispositif dobservation de fluorescence (1) équipé de : une unité dirradiation (3) destinée à irradier une lumière dexcitation et une lumière déclairage sur un objet (F) une unité dimagerie de fluorescence (18) destinée à capturer la fluorescence générée dans le suj
