An endoscope system includes: an insertion portion an observation window provided on the insertion portion to acquire a first subject image from a forward direction an observation window provided on the insertion portion to acquire a second subject image from a lateral direction different from the forward direction an illumination window to emit first illumination light in the forward direction an illumination window to emit second illumination light in the lateral direction an aperture to adjust an amount of light of the first illumination light and an amount of light of the second illumination light a control section to integrate amounts of opening of the aperture to calculate an integrated value and an illumination light amount control section to control the amount of light of the first illumination light and the amount of light of the second illumination light based on the integrated value.
