An endoscope system includes: a light source that is configured to emit primary light; plural illuminators that are configured to be irradiated with the primary light to emit plural respective illumination light generated based on the radiated primary light toward an observation object so that at least part of the plural illumination light overlap on the observation object; and an adjuster that is configured to desirably adjust a ratio of light quantities of the primary light that travels from the light source to the respective illuminators, so as to distribute the primary light to the respective illuminators.