PURPOSE: To clean a roller surface by a blade without resistance, under the state where the toner is softened, by monitoring and detecting always the roller surface temperature and by inhibiting driving of a thermal fixing roller forcedly when this temperature is a prescribed value or less.

CONSTITUTION: Amplifier AMP1 to detect the upper limit temperature of the thermal fixing equipment is connected between output sides (a) and (b) of the bridge-form resistance circuit, where thermoelectric element 6 is connected to one side, and amplifier AMP2 to detect the lower limit temperature is connected between (a) and (c). The output of AMP1 is input to driving circuit 8 of heater 3; and while the output is high-level, the power supply circuit of heater 3 is turned on; and when the output is low-level, the power supply circuit is turned off forcedly. The output of AMP1 is sent to input terminal S of FF1 through NOT gate NOT1, and the output of AMP2 is sent to reset input R of FF1, and main motor 7 is driven and controlled according to the output of FF1. As a result, the toner is prevented completely from exfoliating together with the Teflon layer.