An endoscope system has observation modes making observations with lights having optical characteristics different from each other. The system includes an endoscope including an insertion section provided with an illumination window, a light guide arranged in the insertion section, and including an entrance end on which the lights enter and a plurality of light guide areas that guide the lights entered on the entrance end, and an entrance area switching unit that switches between the light guide areas through which the entered lights are guided by switching between areas on which the lights enter at the entrance end in accordance with an observation mode.
