An endoscope insertion part of an endoscope and a treatment tool insertion part of a treatment tool are insertable through an overtube inserted into a body wall, and a slider is provided for moving the endoscope insertion part and the treatment tool insertion part forward and backward in an interlocking manner. An operating part of the treatment tool includes a guide member that guides a cable part so as to be movable forward and backward in an axial direction so that the cable part of the endoscope is kept from being separated from the surface of the operating part beyond a fixed distance. Accordingly, the cable part can be reliably held down by an index finger of a right hand gripping the operating part, and, the operation of the operating part and the movement operation of the endoscope insertion part can be performed with only a right hand.
