Treatment system 10 includes a high frequency power source 73, a heating power source 83, based on a pair of conductors 52a, 52b and a pair of jaws 36a having a heater member 53, and 36b, a heating power source 83 to the temperature of the heater member 53 By constant temperature control, by using the heating power parameter based on the initial state of change in the heating power that decreases after the maximum value increased after start of the application of the thermal energy, for subsequent of the heating acquires the power reduction patterns that predict changes state of the power acquisition after it is provided with a, a control section 94 that controls so as to pattern control the heating power based on the power reduction pattern.処置システム10は、 高周波電源73と、発熱用電源83と、一対の導電体52a、52bとヒーター部材53とを有する一対のジョー36a、36bと、発熱用電源83をヒーター部材53の温度に基づき定温制御することにより、前記熱エネルギの印加開始後に増加し最大値を示した後に減少する前記発熱用電力の初期の変化状態をもとにした発熱用電力パラメータを用いて、その後の前記発熱用電力の変化状態を予測した電力減少パターンを取得し、取得後は前記電力減少パターンに基づいて前記発熱用電源をパターン制御するように制御する制御部94と、を具備する。
