To reduce a peak power consumption of a plurality of heat sources provided in a fixing part.

An image forming apparatus including the fixing part for thermally fixing developer on a medium includes: a first heat source in which an output of a central part in the longitudinal direction is higher than that of both the ends; a second heat source in which the output of both the ends in the longitudinal direction is higher than that of the central part; and the fixing part heated by the first heat source and the second heat source and configured that the longitudinal direction is disposed in parallel with the first heat source and the second heat source. The image forming apparatus is further provided with: a temperature detecting part for measuring the temperature of the central part in the longitudinal direction of the fixing part; a temperature setting part for storing a first threshold; and a fixing control part, when the temperature measured by the temperature detecting part reaches the first threshold, changing from the heating by the first heat source to the heating by the second heating source to preheat the fixing part.