A laminated packaging material having high impermeability to gases and high workability is prepared by the lamination of a layer of copolymer of vinylidene chloride containing 3-10% by weight of a plasticizer of a number average molecular weight of less than 500 with another layer of a synthetic resin containing 5-70% by weight of at least one organic additive of a number average molecular weight of about 800-10,000 and selected from the group consisting of glycerides of higher saturated or unsaturated fatty acids and of epoxidized fatty acids, rosin and rosin derivatives, oligomeric copolymers of styrene with isobutylene, butadiene or isoprene, oligomeric polyesters which are formed by polycondensation of aliphatic dicarboxylic acid with 6-10 carbon atoms and polyhydric alcohol with 2-6 carbon atoms and have a number average molecular weight of 1,000-2,000, and oligomeric epoxides formed by polycondensation between epichlorhydrin and bisphenol.