A treatment system 1 that can easily perform an appropriate treatment is provided. The treatment system 1 includes a treatment tool 2 having a heating element 13 that applies thermal energy to a living tissue, an element temperature measuring unit 39 that measures an element temperature T1 of the heating element 13, a power source 30 that generates electric power, and an element temperature. A first calculator 33A that estimates the temperature difference ΔT using a table or expression stored in advance to estimate the temperature difference ΔT between T1 and the temperature T2 of the living tissue based on the output value of the power supply 30. And the second calculation unit 33B that estimates the tissue temperature T2 from the element temperature T1 and the temperature difference ΔT estimated by the first calculation unit 33B, and the power source 30 is controlled based on the tissue temperature T2 estimated by the second calculation unit 33B. And a control unit 34.適切な処置を行うことが容易な処置システム１を提供する。 処置システム１は、生体組織に熱エネルギを印加する発熱素子１３を有する処置具２と、発熱素子１３の素子温度Ｔ１を測定する素子温度測定部３９と、電力を発生する電源３０と、素子温度Ｔ１と前記生体組織の温度Ｔ２との温度差ΔＴを電源３０の出力値をもとに推定するために予め記憶された表または式を用いて、前記温度差ΔＴを推定する第１算出部３３Ａと、素子温度Ｔ１と第１算出部３３Ｂが推定した温度差ΔＴとから組織温度Ｔ２を推定する第２算出部３３Ｂと、第２算出部３３Ｂが推定した組織温度Ｔ２にもとづいて電源３０を制御する制御部３４と、を具備する。
