An image forming device includes a heater, a heat application rotation member heated by the heater, a pressure application rotation member heated by the heat application rotation member, a detector configured to detect a surface temperature of the pressure application rotation member, and a controller configured to control a rotation speed of the heat application rotation member and a rotation speed of the pressure application rotation member. The controller varies at least one of the rotation speeds depending on an amount of temperature change or temperature change ratio detected by the detector until the surface temperature of the pressure application rotation member detected by the detector reaches a predetermined temperature.