in a standby state capable of forming an image , a period of a drive pulse of a heater in a fixing unit is made longer than that of the drive pulse in an image formation state to decrease the number of on / off times of a fixing heater , thereby decreasing a brightness flicker in an illumination equipment which is connected to a power supply system identical with that of an image formation apparatus for on / off controlling the heater to control temperature of the fixing unit to be at a target temperature .