PROBLEM TO BE SOLVED : To provide a packaging material for an outer packaging bag of an infusion bag which keeps transparency, gas barrier properties and retort adaptability, is excellent in low elution properties, exhibits a high interlayer adhesive strength and keeps it even after heat sterilization treatment, and prevents occurrence of delamination; an outer packaging bag of an infusion bag composed of the same; and a method for manufacturing the same.SOLUTION : A packaging material for an outer packaging bag of an infusion bag has at least a transparent gas barrier film layer, an adhesive layer and a heat sealable resin layer in this order. The adhesive layer is formed of an adhesive resin composition containing a terpolymer of alkene-(meth)acrylic ester-unsaturated carboxylic acid.SELECTED DRAWING : Figure 1