PURPOSE: To provide a heat-sealing method for a gas barrier laminated film, which has been improved so that a silicon oxide thin film layer can be prevented from being broken, for the heat-sealing method for a gas barrier laminated film which contains a transparent plastic film on the surface of which a silicon oxide thin film layer is formed, and at least on the innermost layer of which a sealant film is laminated.

CONSTITUTION: When a gas barrier laminated film 1, which contains a transparent plastic film on the surface of which a silicon oxide thin film layer is formed, and at least on the innermost layer of which a sealant film is laminated, is heat-sealated by using a heat-seal block 2 with a seal bar 3 consisting of a strap of protruding part, the heat-seal block 2 to be used has a strap of edge part 4 which corresponds to the inside of a sealed part of a product to be sealed, is processed with a radius of curvature of 0.2-3mm.