PROBLEM TO BE SOLVED: To allow, only in a case of having a definite intention, movement of exceeding one end of a normal moving range used when treating body tissue.SOLUTION: A medical treatment instrument includes: a sheath part 3 having a long body 31 and a cylindrical body 32 respectively including distal ends and proximal ends, the cylindrical body in which the long body is slidably inserted a treatment part disposed at the distal end of the sheath part and an operation part 4 provided at the proximal end of the sheath part. The operation part 4 includes a sider part 41 to which the proximal end of the long body is connected a base part 42 to which the proximal end of the cylindrical part is connected and that is slidably attached to the base part and slide regulation means (a button 43) that, when being non-pressed, takes a first attitude of interfering with a part of the base part to regulate one end of the normal moving range of the slider part and, when being pressed, takes a second attitude of releasing the interference to allow movement of exceeding one end of the normal moving range of the slider part.SELECTED DRAWING: Figure 1ACOPYRIGHT: (C)2018,JPO&INPIT【課題】明確な意図がある場合にのみ、体内組織に対する処置の際に用いられる通常移動範囲の一端を越えた移動を許容すること。【解決手段】それぞれ遠位端および近位端を有する長尺体31と該長尺体がスライド可能に挿通された筒状体32とを有するシース部3と、該シース部の遠位端に配置される処置部と、該シース部の近位端に設けられる操作部4とを有する医療用処置具である。操作部4は、長尺体の近位端が接続されるスライダ部41と、筒状体の近位端が接続され、ベース部にスライド可能に取り付けられたベース部42と、非押圧時にベース部の一部に干渉して該スライダ部の通常移動範囲の一端を規定する第1姿勢となり、押圧時に該干渉を解除して該スライダ部の該通常移動範囲の一端を越えた移動を可能とする第2姿勢となるスライド規制手段(ボタン43)とを有する。【選択図】図1A