PROBLEM TO BE SOLVED: To provide an endoscope system, etc. capable of suppressing an unnecessary increase in power consumption attributable to the driving of a light source.SOLUTION: An endoscope system 1 includes: a light source part for supplying illumination light for illuminating a subject a light emission control part for controlling the light source part to cause the light source part to emit light in a predetermined light emission pattern a light detection part for detecting return light of the illumination light poured on the subject, and generating and outputting a signal according to the detected return light a determination part for determining whether or not a first output pattern set based on the predetermined light emission pattern matches a second output pattern acquired by detecting an output state of a signal output from the light detection part when the light source part is emitting light in the predetermined light emission pattern a light volume control part for executing control to set the light volume of the illumination light supplied from the light source part to either a first light volume or a second light volume smaller than the first light volume based on the result of the determination by the determination part.
