The treatment tool insertion tool 20 is a treatment tool insertion tool 20 that is attached to the insertion part 2 of the insertion device 1 to be inserted into the subject and causes the treatment instrument 31 to be inserted into the subject, and is a tubular A treatment instrument guide portion 21 and a treatment tool guide portion detachably provided in a portion of the insertion portion located outside the subject when the insertion portion of the insertion device is inserted into the subject, one end of the treatment tool guide portion is connected, A guiding portion main body 22 having a through hole 22 h, a guiding portion main body 22 having a through hole 22 h, a guiding portion main body 22 having a hole 50 h fixed to one end of the guiding portion main body at a connecting portion between the treatment instrument guiding portion and the guiding portion main body and having a treatment tool inserted therethrough A membrane member 50 that is watertightly engaged with the treatment instrument and that is extensible and retractable and suppresses permeation of the liquid, deformation amount regulating units 22s and 41t that regulate the deformation amount of the membrane member when the membrane member deforms in the longitudinal direction of the treatment instrument .処置具挿通具20は、被検体内に挿入される挿入機器1の挿入部2に取り付けられ処置具31を被検体内に挿入させる処置具挿通具20であって、処置具を案内する管状の処置具案内部21と、挿入機器の挿入部が被検体内に挿入された際に挿入部の被検体外に位置する部位に着脱自在に設けられ処置具案内部の一端が連設され挿通口22pを有する案内部本体22と、処置具案内部と案内部本体との連設部位で案内部本体の一端に固設され処置具を挿通する孔50hを有し該孔に処置具を挿通したとき処置具と水密に係合し伸縮自在で液体の透過を抑制する素材の膜部材50と、膜部材が処置具の長手方向に変形する際の変形量を規制する変形量規制部22s,41tを有する。
