An endoscope system includes a plurality of light sources which emits light having different wavelengths, a photodetector which is provided in each of the plurality of light sources, and which receives a part of the light of the plurality of light sources and obtains information on a light emitting quantity of the plurality of light sources, an image acquisition unit that acquires an image to be observed for each illumination light using at least first illumination light and second illumination light, composed of the light emitted from at least one of the plurality of light sources, and a control unit that makes a mutual image signal ratio constant in the plurality of images acquired by the image acquisition unit.
