PURPOSE: To reduce power consumption of the whole of a copying machine without lowering the efficiency of fixing by constituting a controlling device by giving priority to electric conduction of a heater of fixing roll side over electric conduction of a heater of pressing roll side.

CONSTITUTION: A heater 3 of fixing roll side is on/off-controlled at a set temperature by a fixing roll heater controlling circuit 17 without influenced by a temperature comparator circuit 15 of pressing roll side, and an on-signal of an exposure lamp. On the other hand, when the on-signal of the exposure lamp is outputted, a heater 10 of pressing roller side is turned on or off by a pressing roll controlling circuit 18 under conditions that an output of a temperature comparator circuit 14 of fixing roll side is not made. If the on-signal 16 of the exposure lamp is not outputted, it is inverted by an inverter I2 and an input of high level is given to an input terminal of an AND circuit A2. Accordingly, if there is an output from the temperature comparator circuit 15 of pressing roll side, the heater 10 is conducted irrespective of presence of output of temperature comparator circuit 14 of fixing roller side.