A stapler has a table formed with a clincher mechanism at a front end and is rotatably supported on a frame. A pair of locking plates slidably supported along the frame between the table and the frame prevents the clincher mechanism from rotating in a direction in which the clincher mechanism moves toward a staple driving section. Drive cams are provided independently for each of the locking plates to drive the locking plates. The times at which the respective locking plates are pulled out from between the table and the frame by the respective drive cams are shifted from each other.