The purpose of the present invention is to provide a method of forming a seal-rupture part in a film member forming packaging for packaging an absorbent article, wherein said method allows cuts including perforations, or half-cuts, to be made easily and reliably on the film member and is able to form a gap in a cut portion when cutting the film member. That is to say, a formation step (S4) of forming a seal-rupture part (20) in a film member (2) is performed by applying tension on the film member (2) in the lengthwise direction in a state in which transport of the film member (2) is stopped, and while applying tension, using a laser to make cuts and/or half-cuts at the site on the film member (2) where the seal-rupture part (20) is to be formed.
