A fluorescence observation apparatus (1, 201, 301, 401, 501) comprising: an illuminating section that is adapted to be inserted into a body cavity of a biological organism and to emit excitation light onto an inner wall of the body cavity; an image acquisition section (20, 420) that is adapted to acquire an image of fluorescence generated by the excitation light emitted from the illuminating section so as to acquire image information; and a fluorescent-probe discharging section that stores fluorescent probes adapted so that fluorescence characteristics change by reacting with iNOS existing in the inner wall of the body cavity or so that fluorescence characteristics change by reacting with NO produced by activation of iNOS, wherein the fluorescent probes are adapted to be excited so as to generate the fluorescence generation sites, the fluorescent-probe discharging section being adapted to spray the fluorescent probes to the inner wall of the body cavity, characterized in that the fluorescence observation apparatus (1, 201, 301, 401, 501) further comprises: a counting section that is adapted to count the number of fluorescence generation sites on the basis of the fluorescence included in the image information acquired by the image acquisition section (20, 420); a fluorescence-pattern determining section that is adapted to detect a pattern of each fluorescence generation site and determine whether or not the pattern matches a pattern of aberrant crypt foci, ACF; and a correcting section that is adapted to subtract the number of fluorescence generation sites determined as not satisfying a pattern condition of the ACF by the fluorescence-pattern determining section from the number of fluorescence generation sites counted by the counting section. an illuminating section that is adapted to be inserted into a body cavity of a biological organism and to emit excitation light onto an inner wall of the body cavity; an image acquisition section (20, 420) that is adapted to acquire an image of fluorescence generated by the excitation light emitted from the illuminating section so as to acquire image information; and a fluorescent-probe discharging section that stores fluorescent probes adapted so that fluorescence characteristics change by reacting with iNOS existing in the inner wall of the body cavity or so that fluorescence characteristics change by reacting with NO produced by activation of iNOS, wherein the fluorescent probes are adapted to be excited so as to generate the fluorescence generation sites, the fluorescent-probe discharging section being adapted to spray the fluorescent probes to the inner wall of the body cavity, characterized in that the fluorescence observation apparatus (1, 201, 301, 401, 501) further comprises: a counting section that is adapted to count the number of fluorescence generation sites on the basis of the fluorescence included in the image information acquired by the image acquisition section (20, 420); a fluorescence-pattern determining section that is adapted to detect a pattern of each fluorescence generation site and determine whether or not the pattern matches a pattern of aberrant crypt foci, ACF; and a correcting section that is adapted to subtract the number of fluorescence generation sites determined as not satisfying a pattern condition of the ACF by the fluorescence-pattern determining section from the number of fluorescence generation sites counted by the counting section. a counting section that is adapted to count the number of fluorescence generation sites on the basis of the fluorescence included in the image information acquired by the image acquisition section (20, 420); a fluorescence-pattern determining section that is adapted to detect a pattern of each fluorescence generation site and determine whether or not the pattern matches a pattern of aberrant crypt foci, ACF; and a correcting section that is adapted to subtract the number of fluorescence generation sites determined as not satisfying a pattern condition of the ACF by the fluorescence-pattern determining section from the number of fluorescence generation sites counted by the counting section.