is in the condition shown in fig4 in the condition of step 6 the lower ends of the regulating members 61 a 61 b and the uppermost surface of the sheet s are separated from each other by this separation the regulating members 61 a 61 b can move in the conveyance width direction and the regulating members 61 a 61 b respectively moves to the position of 61 a 1 61 b 1 shown by the dotted line of fig5 step 7 the movements in step 7 are conducted by the drive of motors m 2 m 3 and these movements are movements to a position that corresponds to a position where the sheet discharge position shifts in the conveyance width direction for example a position shifted by 30 mm from the solid line position of fig5 in the dotted line positions 61 a 1 61 b 1 the regulating member 61 b is positioned in the area of the sheet s and the regulating member 61 a is positioned out of area of the sheet s next in step 8 the motor m 1 operates and stops by the sheet detecting signal of the sensor 63 the sheet discharge tray 60 elevates again to the position of fig3 a and 3 b in step 8 although the regulating member 61 a is in out of area of the sheet s because the regulating member 61 b is in the area of the sheet s the regulating member 61 a is in the position which brought into contact with the side edge of the sheet s in the same manner as the regulating member 61 b of fig3.