An objective of the present invention is to facilitate, by a simple configuration, firmly attaching a treatment instrument for endoscope and assistive instrument for endoscope to an endoscope operation part, and easily attaching same to and detaching same from the endoscope operation part. Provided is a treatment instrument for endoscope (100) comprising a treatment instrument operation part (103) which can be anchored in a base (30) disposed in an entry portion (24) of a treatment instrument insertion channel (23) in an endoscope operation part (11) and comprising a flange part (32) formed in a non-circular shape when seen in the axial direction of the treatment instrument insertion channel. The treatment instrument operation part (103) comprises: an opening part (120) which has the same shape as the flange part (32) and through which the flange part (32) can be inserted； an engagement part (121) which engages with the flange part (32) by the treatment instrument operation part (103) being rotated about the central axis of the treatment instrument insertion channel (23) in relation to the endoscope operation part (11) in a state in which the flange part (32) is passed through the opening part (120)； and a contact part (122) which makes contact with a seat (33) in the circumference of the base (30) of the endoscope operation part (11) when the engagement part (121) is engaged with the flange part (32).La présente invention vise à faciliter, par une configuration simple, la fixation ferme d'un instrument de traitement pour endoscope et d'un instrument d'assistance pour endoscope à une partie d'actionnement d'endoscope, ainsi que la fixation et le détachement aisés de ceux-ci à/à partir de la partie d'actionnement d'endoscope. À cet effet, la présente invention concerne un instrument de traitement pour endoscope (100) comprenant une partie d'actionnement d'instrument de traitement (103) qui peut être ancrée dans une base (30) disposée dans une partie d'entrée (24) d'u
