A respective band signal conversion section 101 of the present invention generates WLI-R, WL-G, and WLI-B for generating a normal observation light image and NBI-R, NBI-G, and NBI-B for generating a narrow-band light image from an RGB image signal obtained by irradiation with frame sequential light of a set of a rotary filter 14, and a synthesis circuit 201 synthesizes frame sequential color signals of WLI-R, WLI-G, and WLI-B and frame sequential color signals of NBI-R, NBI-G, and NBI-B. Thus it is possible to simultaneously observe a same living tissue in real time in the normal light observation image and narrow-band light observation with a simple configuration.
