A lesion extracting device having a control unit for changing an amount of the excitation light emitted toward a subject body, a measuring unit for measuring a change in the intensity of fluorescence generated from the subject body with respect to a change in the amount of the excitation light, and an extracting unit for calculating a ratio of the change in the intensity of fluorescence on the basis of a ratio of the change in the amount of the excitation light to the change in the intensity of fluorescence and for extracting a lesion part of the subject body on the basis of the ratio of the changes in the amount of the excitation light to the ratio of the changes in the intensity of fluorescence.