Heat-sealing apparatus

A heat-sealing apparatus comprising:

• tube-forming means for forming a packing material made of a laminate including a synthetic resin layer into a tubular-shape of a container;
• and
• a pair of open-and-closable pressing members with a heating mechanism where each pressing member of the pair is positioned on opposite sides of a tubular packing material filled with fluid, said pressing members forming a sealing zone by applying heat and pressure to the innermost synthetic resin layer of the tubular packing material filled with fluid and forming a container with an interior side adjacent the fluid and an outer side adjacent the pressing members,
• wherein each pressing member has a pressing face, a first groove is disposed in at least one of the pair of pressing members outside of said heating mechanism, and said first groove forms a synthetic resin bulge adjacent to an outer side of a zone to be sealed on the resultant container's interior side when said pressing members apply heat and pressure to the tubular packing material.