To sufficiently accurately carry out a widthwise position control of a traveling web edge sent out from a long winding roll even if a detection sensor is provided at a position far from a position of the long winding roll and further enhance a productivity thereby.

The control device has the detection sensor 11 of a position of the web edge; and a moving means 29 for restoring the position of the web edge to a set position by a detection value of the detection sensor. The detection sensor is provided in the downstream of a guide roller 27 positioned in the downstream in the conveying direction of the web sent out from the long winding roll 24 of a web conveying device. A control means is provide, which is programmed such that an action for operating the moving means for converging the position of the web edge to the set position corresponding to the detection value of the detection result for a predetermined short time and for stopping it for a predetermined long time is repeated at a plurality of times.