PURPOSE: To align the edges of sheets correctly by providing a difference between the speed at which sheet position controlling members spread out and the speed at which they press on the edges of sheets so that the speed at which the edges of sheets are pressed may be smaller without changing the period of one cycle of the oscillation of the sheet position controlling members.

CONSTITUTION: Sheet position controlling members 2a, 2b are pivotally mounted on pivot 4. The oscillating speed of sheet position controlling member 2a is controlled by a cam 5 positioned so that it contacts the sheet position controlling member 2a near its lower end. The sheet position controlling members 2a, 2b are caused to move back and forth between the intended sheet position E and th anticipated sheet position F which forms somewhat wider width than E does. The speed at which the sheet position controlling members 2a, 2b move from F to E is made lower than the speed at which said members 2a, 2b move from E to F.