An endoscope system in accordance with the present invention comprises a plurality of endoscope modules having different treatment instruments mounted therein, an endoscope to which the endoscope modules can be attached, and a coupling member fixed to the distal part of an insertion unit of the endoscope and used to make the plurality of endoscope modules freely exchangeable. The plurality of endoscope modules having the different treatment instruments mounted therein are freely exchangeable to be coupled to the distal part of the insertion unit of the endoscope.
