To provide an image forming device which improves the image quality by suppressing defects of fixing or occurrence of creases even in the case of change of a paper classification or switching of resolution setting or at the time of using special paper or the like.

A control part is provided which can temporarily stop a heat discharge fan by paper classifications or can freely switch its rotation control and can freely vary a fixing set temperature in a paper feed mode or a standby mode to a high or a low temperature. If normal ordinary paper is fed at the previous time and thin transfer paper is fed at the present time, the control part holds paper feed till reduction of the fixing temperature and rotates the heat discharge fan for a prescribed time at a higher speed than the normal paper feed state to quickly reduce the fixing temperature to a prescribed temperature. If thin transfer paper is fed at the previous time and normal ordinary paper is fed at the present time, the control part stops the heat discharge fan.