To provide an image forming apparatus that prevents occurrence of downtime due to warming-up of a post-processing device and also prevents delaying of start time for processing each of jobs to be processed.

This image forming apparatus reserves a job that can not be performed at present until warming-up of the post processing device is completed, and performs a job that can be performed at present and can be divided, on a priority basis (S9). In addition, when the warming-up is completed during the processing of the job started on a priority basis, the image forming apparatus divides the job, interrupts processing of the job, and starts processing of the reserved job (S13 to S15).