An image processing device processes jobs to be executed by an image forming device incorporating a fixing unit. The image processing device receives a plurality of jobs. Based on an attribute of each of the plurality of jobs, the image processing device determines, out of the plurality of jobs, at least one job for which fixing can be performed after heating of the fixing unit is stopped and for which fixing is performed after fixing for another job is finished. The image processing device reorders the processing of the plurality of jobs so that fixing is performed for the at least one job after the fixing for the other job is finished. In this way, an image processing device and a method of controlling an image processing device can be provided where power consumption can be reduced.