This small-diameter endoscope surgical instrument comprises: an inner pipe 20 that has an outer diameter equal to that of a small-diameter endoscope 10 to be used, that is used for inserting the small-diameter endoscope surgical instrument into a body, and that is replaced with the small-diameter endoscope 10 after insertion thereof； a guide pipe 30 which is configured to have the small-diameter endoscope or the inner pipe inserted therethrough and which supports the small-diameter endoscope or the inner pipe so as to be movable in an axial direction； and a treatment pipe 40 which is configured to have the guide pipe inserted therethrough to support the guide pipe so as to be movable in the axial direction, and which has, at the leading end thereof, a treatment means such as an electrode, a blade, or a hook, wherein each of the small-diameter endoscope, inner pipe, guide pipe, and treatment pipe has an independent operation part at the proximate end thereof, and thus the rotation angle and the position in the axial direction thereof can be changed. The present invention enables, with a simple configuration, gripping or fixing of tissues, electrocautery, electrocoagulation, ablation, mobilization, separation, or traction of tissues, and further enables removal of blood clots, etc., stuck to a hook during surgery, and a sample extraction for biopsy.Cet instrument chirurgical endoscope de petit diamètre comprend : un tube interne 20 qui a un diamètre externe égal à celui d'un endoscope de petit diamètre 10 à utiliser, qui est utilisé pour introduire l'instrument chirurgical endoscope de petit diamètre dans un corps, et qui est remplacé par l'endoscope de petit diamètre 10 après son insertion ； un tuyau de guidage 30 qui est configuré pour avoir l'endoscope de petit diamètre ou le tuyau interne inséré à travers celui-ci et qui supporte l'endoscope de petit diamètre ou le tuyau interne de façon à être mobile dans une direction axiale ； et un tuyau de traitement 40 qui es
