Image capture is performed while broadband and narrow band light are simultaneously emitted to tissue site. B pixel sensing the narrow band light outputs a summed image signal having a brightness value of a B component of the broadband light and a brightness value of the narrow band light. G and R pixels, not sensing the narrow band light, output broadband image signals having brightness values of G and R components of the broadband light, respectively. Based on correlation information and the G component of the broadband light, the brightness value of the B component of the broadband light is obtained. The obtained brightness value is subtracted from the summed image signal to separate the brightness value of the narrow band light therefrom. A broadband image and a narrow band image are generated from the broadband image signals and the narrow band image signal, respectively.