There is provided a treatment system 1 with a good operability. The treatment system 1 has: a treatment instrument 2 applying treatment energy to living tissue； a power source 30 outputting power； a temperature measuring section 39 for measuring a temperature of the living tissue； a calculation section 33 calculating a heating amount Q, which is a time integral value of the temperature of the living tissue, from the temperature of the living tissue and a time period of applying the treatment energy； a comparison section 34A comparing the heating amount Q and a predetermined heating amount setting value Qset； and an instruction section 34B giving an instruction based on a result of the comparison by the comparison section 34A.
