to an organic part 1 and takes a normal image of the organic part 1 formed by the white light wh while propagating an auto fluorescence image formed by auto fluorescence emitted from the organic part 1 upon excitation by the exciting light the normal image taken by the front end portion 200 is taken in by an image take in section 300 the image take in section 300 takes in the normal image as image data and stores the image data further the image take in section 300 receives the fluorescence image divides the fluorescence image into three wavelength ranges and stores the three pieces of image data corresponding to the three wavelength ranges a characteristic obtaining means 400 obtains two pieces of image data corresponding to a pair of characteristic values from the pieces of image data stored by the image take in section 300 the two pieces of image data obtained by the characteristic obtaining means 400 is input into a recognizing section 500 and the recognizing section 500 carries out a logical operation for recognizing change of the tissue condition due to a disease on the basis of the two pieces of image data and outputs the result of the operation.