A treatment system 1 includes a treatment instrument 2 that has a pair of freely openable/closable holding sections 10 for applying thermal energy generated by a heat generation section 20 to a living tissue LT held between the holding sections, a signal output section 31 that supplies an alternating current drive signal to the heat generation section 20, a setting section 32 that sets a target temperature of the heat generation section 20, a signal detection section 33 that detects a current and a voltage of the drive signal, a control section 34 that controls a temperature of the heat generation section 20 by adjusting power of the drive signal, a signal extraction section 35 that extracts a direct current component from the drive signal detected by the signal detection section 33 and a fault detection section 36 that detects a precursory phenomenon of a fault of the heat generation section 20 based on an extracted signal extracted by the signal extraction section 35.
