PURPOSE: To display lapse of warming-up time till a copying machine reaches a stable region and to eliminate wasteful wait time, by controlling plural displays in accordance with detection of heater roller temperature.

CONSTITUTION: An output issued from a thermistor 1 by detecting temperature of a heater roller is applied to calculation amplifiers 101W105 in parallel forming comparators set to different reference voltages with resistances 106W110, etc. of a display control circuit 100. As a result, the transistors of a driver 112 are caused to conduct in succession in accordance with the temperature to control lighting of corresponding LED 11W15, thus permitting wasteful wait time to be eliminated by displaying lapse of the warming-up time till reaching the stable region with these LED11W15.