Print jobs having a mixture of first image sheets and second image sheets are sorted to a first image forming device and a second image forming device. After image formation is performed on sheets by the respective image forming devices, radio frequency IC tags (RFID tags) are affixed to the sheets, in which attribute information including post-processing information and page identification information is written. Sheet bundles produced by the respective image forming devices are separately set to a post-processing device. The post-processing device reads out the attribute information stored in the radio frequency IC tags, and the sheets are selectively fed from the respective sheet bundles while conforming to the page order. Thereafter, the post processing is performed.