To provide a paper sheet post-processing device capable of easily and properly setting folding condition in folding a paper sheet printed with an image, and to provide an image forming device, an image forming system, a paper sheet post-processing control method, a paper sheet post-processing control program and a recording medium.

In this image forming system 1, the post-processing device 50 carries out folding of paper sheets discharged from the image forming device 10 based on the folding condition obtained by reading folding condition setting mark sheets MS1 and MS2 or the like, and performs processes for storing and reading the folding condition into/from a folding condition storage non-volatile memory in response to an instructed operation by an operation display section 16. Consequently, even in a method with a large number of folding conditions, the folding conditions can be easily and properly specified and set.