A treatment system 10 includes: a high-frequency power source 73 a power source for heat generation 83 one pair of jaws 36a, 36b having one pair of electric conductors 52a, 52b and a heating element 53 and a control section 94 which performs constant temperature control on the power source for heat generation 83 on the basis of temperature of the heating element 53 and performs control so as to finish application of the thermal energy if the power for heat generation, which increases after application of the thermal energy starts and decreases after a maximum value is exhibited, becomes not more than threshold power or if a rate of decrease in the power for heat generation becomes not more than a threshold rate.
