An image forming apparatus includes a feeder having a longer side direction orthogonal to a conveyance direction of a recording medium, and feeds a maximum size recording medium with a longer side first, an image forming unit having a maximum sheet feed width corresponding to a longer side length of the maximum size recording medium, and prints a toner image onto the recording medium, and a sub feeder that can feed the maximum size recording medium to the image forming unit independently from the feeder. A post processing apparatus receives a printed recording medium and executes post processing on a side of the recording medium. A feeding source of the maximum size recording medium is selected from the feeder and the sub feeder for executing the post processing on the longer and shorter sides of the maximum size recording medium, respectively.