To provide a heat treatment device which can perform an output control other than a constant temperature control to expand the range of options in treatment.A heat treatment device 1 includes a coagulation dissection forceps 2 having a heat generation element 21 in a treatment portion 9, an applied current detection section 31 and an applied voltage detection section 32 which detect values of a current and a voltage applied to the heat generation element 21, a control operation section 33 which performs one operation out of a current, a voltage, a power, and a temperature at the heating element 21 using respective detection results of the applied current detection section 31 and the applied voltage detection section 32, an output setting section 35 which performs one setting out of the current, the voltage, the power, and the temperature at the heating element 21, an output control section 36 which controls an output to the heating element 21 based on the operation result by the control operation section 33 and the setting of the output setting section 35, and a control selection switching section 39 which selects one or more control out of a constant current control, a constant voltage control, a constant power control, and a constant temperature control as a control content of the output control section 36.
