A fluorescence diagnosis endoscope system used to observe human tissue is provided. The system has a light source for illuminating the human tissue with normal light and excitation light having a certain wavelength range. The human tissue fluoresces in response to illumination with the excitation light. The system further has a pair of image receiving elements for outputting image signals corresponding to received optical images. A filter which transmits only light produced by the fluoresced human tissue is provided in front of one image receiving element. The image signals output by the image receiving elements are selectively processed and transmitted to a display.