Provided is an endoscopic-treatment-instrument operation input device (1) that includes: a grip section (5) that is shaped so as to be capable of being gripped by the palm and at least the little finger and the ring finger of one hand (H) of an operator； an operation section (6) that is arranged at a position so as to be operable by the thumb of the one hand (H) in state where the grip section (5) is being gripped and that allows an operation command for causing a joint of the treatment instrument to actuate to be input； and a frictional fixing section (7) that presses, and fixes in place with friction, a position midway along elongated trunk section (4a) of the treatment instrument in the longitudinal direction through use of the index finger of the one hand (H).
