An endoscope system includes an endoscope having an insertion tube; a main light source; an auxiliary light source; and a fiber-optic light guide provided in the insertion tube, the fiber-optic light guide being provided with an incident end face which selectively faces one of the main light source and the auxiliary light source, and an exit end face which faces an illuminating optical system provided at a distal end of the insertion tube. The auxiliary light source is a white LED.