Image forming apparatus with highly operable sheet discharge device

An image forming system including a sheet processing device and an image forming apparatus, said sheet processing device comprising:

• a memory which stores identification information of a user requesting a job corresponding to each job,
• a first discharge tray,
• a plurality of second discharge trays,
• a transport unit which transports a bundle of sheets discharged on said second discharge trays to said first discharge tray, and
• a controller which controls said transport unit so as to transport from said second discharge tray a bundle of sheets by a previous job when a user of a new job differs from the user of the previous job in discharging a sheet by the new job to said second discharge tray already storing a sheet by the previous job.

A sheet discharge method of a sheet processing device including a transport unit transporting a bundle of sheets from a plurality of second discharge trays to a first tray, said method comprising the steps of:

• selecting at least one second discharge tray from a plurality of second discharge trays,
• discharging a first bundle of sheets to said selected second discharge tray,
• determining whether a second bundle of sheets correspond to a user of said first bundle of sheets,
• transporting the first bundle of sheets from said second discharge tray to said first tray when determination is made of the same user, and
• discharging the second bundle of sheets to said selected second discharge tray after the end of transportation.