PURPOSE: To inform a holding state without giving troublesomeness, by gradually decreasing a flickering period of a pilot lamp in accordance with a time variation extending from start of heat fixing to completion of the holding state.

CONSTITUTION: When a main switch 14 is turned on, a fixing heater 16 is heated, and resistance of a thermistor 20 drops. Accordingly, a collector current of TRs 22, 32 increases. When the TR22 conducts, discharge of a capacitor 24 is started, and as for a repeated cycle of ON-OFF of discharge of a timer 26, it is repeated quickly since a resistance value of the TRs 22, 32 decreases as time passes. Also, an output state inverted operation cycle of a comparator 34 is also shortened as it gets near completion of a holding state. As a result, a flickering time of a pilot lamp 28 decreases. In this way, a time before completing the holding state is visually confirmed without giving troublesomeness.