A gas barrier laminate comprising: a plastic substrate (I); a gas barrier layer (II) formed from a gas barrier layer-forming coating material (C) containing a polyalcohol-based polymer (A) and a polycarboxylic acid-based polymer (B); and an overcoat layer (III) formed from an overcoat layer-forming coating material (F) containing at least one of a monovalent metal compound (D) and a bivalent or higher metal compound (E); wherein the gas barrier layer (II) is laminated to the plastic substrate (I), either directly or with an anchor coat layer disposed therebetween, the overcoat layer (III) is laminated on top of the gas barrier layer (II), and when a laminated product is prepared by laminating a laminate adhesive layer (IV) and a heat seal layer (V), in that order, to either the overcoat layer (III) or the plastic substrate (I) of the gas barrier laminate, either directly or with a printing ink layer disposed therebetween, the lamination strength (X) of the laminated product is not less than 1 N/cm, and the ratio of the lamination strength (Y) following a hot water treatment for 30 minutes at 95.degree. C. relative to the lamination strength (X) (namely, Y/X) is not less than 0.3.