A sheet finisher of the present invention includes jogger fences for jogging sheets sequentially stacked in a stapling section, and a stapler for stapling the sheets together. A CPU (Central Processing Unit) controls a jogger motor such that the jogger fences each move to a first position (L1), a second position (L2), and a third position (L3) in accordance with the width of sheets in a direction perpendicular to the direction of sheet conveyance. The first position is remote from the edge of a sheet stack in the direction of the width by a preselected amount. The second position is closer to the edge than the first position by a preselected amount and slightly overlaps the edge. At the third position, when the stapler staples the sheet stack, the jogger fence substantially contacts the edge in accordance with the width.