PURPOSE: To enhance a tearing resistance by laminating a layer of a sealing material for bonding a reinforcing sheet material to a container, a layer of a material impermeable to air and moisture, and a layer of the reinforcing material, thereby increasing a strength of the sheet material.

CONSTITUTION: The reinforcing sheet material 10 for sealing comprises a layer 12 of a sealing material (for example, a heat sealable film), a layer 14 of a material (e.g. a polyvinyl chloride, aluminum foil) substantially impermeable to air and moisture, and a layer 16 of a reinforcing material. The layer 16 is obtained by laminating at least two single layers made of uniaxially oriented films together by intersecting a strong direction of the one single layer to a weak direction of the other single layer to impart the same strength in all directions by increasing tearing and tensile strengths in a mechanical direction, its cross sectional direction and oblique direction.