A grasping treatment unit includes a first jaw, and a second jaw openable and closable relative to the first jaw. In the first jaw, a heating wire continues without branching from a first extending end to a second extending end, and heat is generated over an entire length from the first extending end to the second extending end when the electric current flows through the heating wire. In a heating portion, a calorific value per unit area is higher in a distal portion than in a proximal portion in the first jaw when the heat is generated from the heating wire. On a treatment surface of the first jaw, an amount of heat transfer from the heating portion is greater in the distal portion than in the proximal portion.