In the light source unit 3A, a switching filter section 14, which can switch the RGB filter for normal-light observation and a filter for fluorescent observation on the optical path, is installed in front of the lamp 12, where if the fluorescent image mode is selected, the excitation light in a part of the blue wavelength band is supplied to the electronic endoscope 2A, and the excitation light reflected by the subject side is shielded by the excitation light cut filter 27 in front of the CCD 28 so as to obtain the fluorescent image, and also the signal of the fluorescent image and the signals of the two reflected light images which are set in a predetermined wavelength band are passed through the image processing circuit 38, where a matrix circuit for appropriately allocating the color signals of the R, G and B channels is installed, and as a result, the images can be displayed on the monitor 5 in pseudo-colors in hues which allow easy identification of a normal tissue and a pathologically affected tissue.