An endoscope system includes: an insertion portion insertable into a body cavity of a subject an illumination fiber guiding light caused to be incident on a proximal-end-side end face, to a distal-end-side end face a light-receiving fiber group guiding light from the subject and emitting the light a light source portion generating illuminating light a light detecting portion a first optical unit capable of changing an optical path of the illuminating light caused to be incident on the proximal-end-side end face of the illumination fiber a second optical unit capable of changing the optical path for the illuminating light changed by the first optical unit and causing the illuminating light to be incident on the light-receiving fiber group and a control portion performing control of whether or not to change the optical path in the first optical unit and the second optical unit.
