To display the shift tendency of a peak wavelength of the fluorescence intensity generated from a measured site irradiated with excitation light as an information source for estimation of tissue properties by observer.

An excitation light L2 from GaN semiconductor laser 114 is irradiated on the biological measurement site 10 and the generated fluorescence L3 is received via an image fiber 103 by a CCD image sensor 125 with an on- chip mosaic filter 123 composed of filters with transmission wavelength band about 480 nm and about 500 nm respectively. A1/A2 computing section 128 calculates the ratio of the light intensity A1 near 480 nm and the light intensity A1 near 500 nm A1/A1 for each image element of the CCD image sensor. The comparison section 131 compares A1/A2 with a reference value RA previously decided based on the fluorescence from a normal tissue and a diseased tissue and displays the compared results deciding that if the A1/A2 is larger, the peak wavelength shifts toward the peak wavelength of fluorescence from the normal tissue and if smaller, it shifts toward the peak wavelength of diseased tissue.