A compressed air is ejected from air ejector ports (14) to between a mold surface defining cavity (12) of mold (7) and a surface of a hot melt resin layer after starting to fill or inject the hot melt resin material into cavity (12) and before a temperature of the hot melt resin material becomes equal to or lower than a softening point thereof. Recesses (Q) are formed by positively generating a “sink mark” on a surface of edge protector (6) by ejection of the compressed air, and at the same time, gap (G) is formed between the surface of edge protector (6) and the mold surface. As a result, when bead-shaped edge protector (6) is integrally formed in long-side heat-fused portions (5c) of laminated-film exterior package case (5) by using a thermoplastic hot melt resin material, mold releasability of the molded edge protector from the mold can be enhanced.