A treatment device includes a longitudinal member having a longitudinal axis, a pair of jaws installed at a distal end of the longitudinal member and configured to be opened and closed in a direction crossing the longitudinal axis of the longitudinal member by being operated to open and close, a first grasping member supported by a first jaw of the pair of jaws and including a linear members annularly curved within a plane crossing an opening-closing direction of the jaws, a second grasping member supported by a second jaw of the pair of jaws and configured to open and close with respect to the first grasping member with an open-close motion of the pair of jaws, the second grasping member configured to apply a grasping force with the first grasping member to an object to be grasped when the second grasping member is closed.
