A surgical treatment instrument comprising: an insertion portion; an operation portion provided at a proximal end of the insertion portion; a treatment portion provided so as to extend from a distal end of the insertion portion; two gripping members (308, 326, 331) provided on the treatment portion, each having a gripping face (326c, 331a); an open/close operating member provided at the operation portion and operatively coupled with at least one of the two gripping members (308, 326, 331) to perform opening/closing by at least one of the two griping members (308, 326, 331) being moved; a variable angle operating member provided on the operation portion to change the treatment portion to a predetermined angle; a braked member provided within the operation portion and operating in conjunction with the operation of the variable angle operation portion; a plate spring that presses the open/close operating member in a direction to separate from the braked member, braking means provided at the plate spring and within the operation portion to brake the braked member by operating in conjunction with the operation of the open/close operation member; wherein the open/close operating member is adapted, when the open/close operating member is displaced to an operation position by being operated against a pressing force of the plate spring to perform the opening/closing by at least one of the two gripping members (308, 326, 331) being moved, to simultaneously press the braking means toward the braked member in conjunction with bending of the plate spring so that friction resistance on the braked member is increased to stop the movement of the braked member and brake a movement of the variable angle operative member to thereby maintain a predetermined angle of the treatment portion, and wherein the open/close operating member is adapted, when the operation of the open/close operating member is discontinued and displaced from the operation position to a non-operation position by being pressed by the plate spring, to simultaneously operate the braking means in conjunction of restoration of the plate spring so that pressing on the braked member is discontinued and the friction resistance is lowered to make the braked member movable and allow the variable angle operating member to move. an insertion portion; an operation portion provided at a proximal end of the insertion portion; a treatment portion provided so as to extend from a distal end of the insertion portion; two gripping members (308, 326, 331) provided on the treatment portion, each having a gripping face (326c, 331a); an open/close operating member provided at the operation portion and operatively coupled with at least one of the two gripping members (308, 326, 331) to perform opening/closing by at least one of the two griping members (308, 326, 331) being moved; a variable angle operating member provided on the operation portion to change the treatment portion to a predetermined angle; a braked member provided within the operation portion and operating in conjunction with the operation of the variable angle operation portion; a plate spring that presses the open/close operating member in a direction to separate from the braked member, braking means provided at the plate spring and within the operation portion to brake the braked member by operating in conjunction with the operation of the open/close operation member; wherein the open/close operating member is adapted, when the open/close operating member is displaced to an operation position by being operated against a pressing force of the plate spring to perform the opening/closing by at least one of the two gripping members (308, 326, 331) being moved, to simultaneously press the braking means toward the braked member in conjunction with bending of the plate spring so that friction resistance on the braked member is increased to stop the movement of the braked member and brake a movement of the variable angle operative member to thereby maintain a predetermined angle of the treatment portion, and wherein the open/close operating member is adapted, when the operation of the open/close operating member is discontinued and displaced from the operation position to a non-operation position by being pressed by the plate spring, to simultaneously operate the braking means in conjunction of restoration of the plate spring so that pressing on the braked member is discontinued and the friction resistance is lowered to make the braked member movable and allow the variable angle operating member to move.