To perform a precise sectioning processing without performing a special sectioning operation when image forming processing is performed a plurality of times by determining an empty discharge stacker among a plurality of discharge stackers, and discharging an image-formed sheet to be newly processed to this stacker.

In an image forming processing device having a discharge port 1012 set in three positions and the same number of discharge stackers 1013 (1013a-1013c) to discharge ports 1012a-1012c, a sheet detecting sensor for detecting the presence of a received printed sheet (hereinafter referred to as sheet) S is provided in each discharge stacker 1013. An optional empty discharge stacker 1013 in which no sheet S is stacked is selected from a plurality of discharge stackers 1013 as the designation of the sheet S to be newly image- processed. According to this, the independently processed sheets S can be prevented from being included in the same discharge stacker to facilitate the subsequent sectioning processing.