An endoscope system includes an illumination unit which includes a modulation section configured to control a visible light source so that visible light from the visible light source is subjected to intensity modulation in a predetermined pattern, and emits modulated visible light as illumination light, a detection section configured to detect the modulated visible light, and a determination section configured to determine whether an insertion portion of an endoscope is present in an object based on a detection result of the detection section. The illumination unit is arranged outside the object, and the detection section is arranged at the insertion portion.
