PROBLEM TO BE SOLVED: To provide a surgical treatment instrument which functions as a bipolar electrocautery, the surgical treatment instrument being appropriately adaptable to the shape and size of an organism tissue to be gripped.SOLUTION: One gripper member 19a constituting the gripper 19 of the surgical treatment instrument includes an arm portion 77 and a first electrode portion 80a rockably arranged with respect to the arm portion 77. The other gripper member 19b is constituted as a second electrode portion 80b facing the first electrode portion 80a. An insulation part 82 which insulates a portion on the proximal end of the first electrode portion 80a from the second electrode portion 80b when the organism tissue is gripped at the distal end of the gripper 19, is arranged at least one of the first and second electrode portions 80a, 80b.
