PURPOSE: To enable accurate temperature control over a heat fixation part by setting a comparison reference time according to at least one of the input voltage and the temperature of the heat fixation part after power-on operation which affect the rising time of the temperature.

CONSTITUTION: A continuous electric feeding limit time is set by storing the ROM of a CPU 8 with a table of continuous electric feeding limit time data predetermined by the relation between the temperature of a fixing roller and the input voltage to a fixing heater 2 which affects the rising time of the temperature of the fixing roller and reading corresponding continuous electric feeding limit time out of the ROM according to the temperature of the fixing roller and the input voltage to the fixing heater 2 which are detected when a power switch is turned on. Thus, the comparison reference time as the reference of the temperature control is set according to at least one of the input voltage and temperature of the heat fixation part after power-on operation which affect the rising time of the temperature. Consequently, the temperature control over the heat fixation part is accurately performed.