To provide an image forming device which is capable of operating heat discharging means efficiently and is excellent in reliability.

In the power consumption saving mode of an image forming device, it is possible to operate a heat discharging fan efficiently by preventing the overshooting of a fixing temp. while making the heat discharging fan perform heat discharge until the temp. of a fixing unit is lowered to a heat discharging fan stopping temp. T-L and also reducing the noise and the power consumption of the heat discharging fan while preventing the longer operation than required of the fan in a state in which the temp. of the fixing unit is lowered by performing a control lowering the temp. of the fixing unit while turning the fixing heater of the fixing unit OFF and, at the same time, by performing a control stopping the operation of the fan based on the result of the comparison between the detection temp. of the fixing unit and the preliminarily set heat discharging fan stopping temp. T-L or of the comparison between a count time after the device entered into the power consumption saving mode and a preliminarily set time t-f.