PURPOSE: To permit the simple assortment even if the paper size is different by installing a discharged paper detecting means for detecting the left edge or the right edge of the discharged paper sheet, at the arrangement part of a paper discharge means.

CONSTITUTION: Though, in job separation, the left side edge of a discharged paper sheet P1 is detected by a reflection type sensor 29a at the left side, the upper and lower roller shafts 17 and 19 shift leftward through a worm gear 23 and a slide gear 22 by the turn of a driving motor 24 which is controlled by a control signal control part 30 so that the discharged paper sheet P1 is shifted leftward until the left side edge is detected. When the paper discharge is completed, the motor 24 stops, receiving the signal supplied from the control signal control part 30. Further, the driving motor 24 is revolved reversely by the control signal control part 30, and the upper and lower roller shafts 17 and 19 are shifted rightward through the worm gear 23 and the slide gear 22, and the upper and lower paper discharge rollers 16 and 18 shift so that the next copying paper is discharged rightward.