An image forming apparatus which makes it possible to perform image forming processing and post-processing efficiently. A job controller divides a single print job into a plurality of print jobs according to the processing capability of a post-processing apparatus. A print controller causes a printer section to perform sequential operations according to the split print jobs, to form a plurality of sets of printed sheet bundles. The sets of sheet bundles formed in association with the respective print jobs and stacked on a stacker by the operation of the print controller are sequentially brought to the post-processing apparatus, and the post-processing apparatus sequentially performs post-processing on the supplied sets of sheet bundles.