To correctly determine whether sheets can be collectively discharged to a delivery tray in units of print job data or not.
Sheet thickness information representing sheet thickness of sheets stored in a plurality of sheet feed trays is previously stored in a secondary storage part 33 on a paper feed tray basis; the stacking height of the sheets stacked on the delivery tray is detected by a sheet sensor 24, the stacking height of the sheets discharged to the delivery tray when an image forming process is executed based on print job data is estimated based on the sheet thickness information and the print job data (step 106 and step 108); residual stacking height of sheets subsequently stackable on the delivery tray is found based on the detected stacking height; and it is determined whether or not all the sheets discharged by the image forming process based on the print job data can be stacked on the delivery tray by determining whether the estimated stacking height is not greater than the residual stacking height or not (step 112).
NISHI MASAAKI
NARITA SACHIKO
ARIJI MASAYOSHI
Kato Kazunori
Katsuichi Nishimoto
Hiroshi Fukuda