The purpose is to reduce correction errors and acquire quantitative information of an object. Provided is a fluorescence observation device (100) including: a light source (10) a fluorescence-image generation part (41) that acquires a fluorescence image (G1) of an object F irradiated with excitation light a white-light-image generation part (42) that acquires a white-light image (G2) of the object F irradiated with illumination light an image correction part (43) that generates a corrected fluorescence image (G3) from these images (G1 and G2) a threshold setting part (45) that sets a threshold based on the average of gradation values of the entire image (G3), a first coefficient therefor, the standard deviation of the gradation values of the image (G3), and a second coefficient therefor an extraction part (47) that determines and extracts a region in the image (G3) that has a gradation value exceeding the threshold, as a region of interest a monitor (50) that displays the region of interest and the image (G2) in association with each other and an input section (53) through which an observer inputs a result as to whether the determination made by the extraction part (47) is right or wrong, in which the threshold setting part (45) sets at least one of the first coefficient and the second coefficient so as to reflect the input result input through the input section (53).
