A grasping treatment instrument includes a sheath, a first grasping piece provided at a distal end of the sheath, a second grasping piece and a movable member. The second grasping piece is connected to the sheath at a first rotation axis perpendicular to a longitudinal axis of the sheath. The movable member is connected to the second grasping piece at the second rotation axis parallel to the first rotation axis, and is configured to move along the longitudinal axis. The first rotation axis is configured to move within the sheath or the second grasping piece in a plane perpendicular to the first rotation axis. The second rotation axis is configured to move within the movable member or the second grasping piece in a plane perpendicular to the second rotation axis.