To suppress the amount of increase of notch length in a notch part for increase of speed of a metallic web by changing the notch length in the notch part formed on the metallic web.

A controller operates a notch formation device 22 when changing slit width of the web 12 to form the notch part 70 on the web 12. At this time, notch length along the direction of conveyance of the notch part 70 is set to length substantially proportional to disposal width Wc of a lug part 15 to be cut off from the web 12 by a shearing member 26. The controller operates only a first notcher 62 in accordance with notch length and forms only a main notch part by the first notcher 62 to use it as the notch part 70 or form the notch part 70 on the web 12 by operating a second notcher 64 at predetermined timing after operating the first notcher 62 and overlapping a part of an auxiliary notch part formed by the second notcher 64 in the main notch part.