A grasping treatment instrument (1) includes a sheath (5), a first grasping piece (13) provided at a distal end of the sheath (5), a second grasping piece (14) and a movable member (17). The second grasping piece (14) is connected to the sheath (5) at a first rotation axis (51) perpendicular to a longitudinal axis (C) of the sheath. The movable member (17) is connected to the second grasping piece (14) at the second rotation axis (52), and is configured to move along the longitudinal axis (C). The first rotation axis (51) is configured to move within the sheath (5) or the second grasping piece (14) in a plane perpendicular to the first rotation axis (51). The second rotation axis (52) is configured to move within the movable member (17) or the second grasping piece (14) in a plane perpendicular to the second rotation axis (52).
