A seaming apparatus is formed from an elongated plate that is inextendible in both longitudinal and lateral directions. An upper surface of the plate is divided into multiple, transversely spaced and longitudinally extending zones. In the preferred embodiment, three such zones, including two edge zones spaced by a central zone, are provided. Numerous elongated upstanding sharp projections are provided in each of the edge zones and an adhesive layer is provided in the central zone. A peelable protective cover is arranged atop the adhesive layer. A thin adhesive layer with a peelable protective cover may be placed on a lower surface to secure the seaming apparatus to a supporting surface.

In the present invention, one surface of a belt-shaped sheet laminate (10), in which a plurality of sheets are laminated, is pressed against a support member (21) having a light passage section (27) through which a laser beam (30) can pass, and the belt-shaped sheet laminate (10) is irradiated, from the support member (21) side via the light passage section (27), with a laser beam (30) to cut and fusion-bond the belt-shaped sheet laminate (10), thereby sealed edge sections (4) are formed by fusion-bonding the edge sections of the plurality of sheets.