An object of the present invention is to correct the deviation of a sheet in the width direction occurring on a conveyance path from a sheet correction mechanism (4) to a discharge tray. A sheet shift portion (41, 43, 44) moves a sheet in the width direction. A conveying position detecting portion (45, 46, 47) detects the position of the sheet in the width direction. A discharge position detecting portion (54, 8a) detects a discharge position of the sheet, in the width direction, discharged onto a discharge tray (33) in a sheet discharge portion (31). A control portion (8b) derives an amount of deviation between the discharge position and a discharge reference position based on a detection result of the discharge position detecting portion (54, 8a). Furthermore, the control portion (8b) corrects a conveying position of the sheet in a sheet conveying portion according to the amount of deviation.