An endoscope operating instrument system which includes a back-and-forth movement mechanism for providing a back-and-forth movement drive force required to operate a forceps located at a distal end of the operating instrument and an insertion/withdrawal mechanism designed to insert and withdraw the insert section via an endoscope channel. A winding unit for winding the insert section of the operating instrument is provided and the insertion/withdrawal mechanism is adapted to insert and withdraw the insert section by rotating the winding unit together with the back-and-forth movement mechanism. Thus, a compact system structure is obtained.