In order to provide information for supporting doctors, on the basis of the oxygen saturation of an observation target, this endoscope system comprises: a light source device; an image sensor; an oxygen saturation calculation unit; a distribution pattern generation unit; a patient condition score calculation unit; and a monitor. The light source device irradiates light on to the observation target. The image sensor captures an image of the observation target by using reflected light from the light and outputs an image signal. The oxygen saturation calculation unit calculates the oxygen saturation of the observation target on the basis of the image signal. The distribution pattern generation unit generates a distribution pattern indicating the oxygen concentration distribution. The patient condition score calculation unit calculates a condition score indicating the condition of the observation target, on the basis of the distribution pattern. The monitor displays the condition score or information on the basis of the condition score.