There is provided a polymer film which includes: a base film layer including a polyamide-based resin having a particular relative viscosity and a copolymer including a polyamide-based segment and a polyether-based segment having a specific content; and an adhesive layer formed on at least one side of the base film layer, wherein a ratio of the melt viscosity of the copolymer to the melt viscosity of the polyamide resin is 0.65 to 1.2 at a shear rate of 1000 s−1 and a temperature of 260° C.