The present invention relates to: a method for manufacturing a polymer film, the method including a base film forming step for co-extruding a first resin containing a polyamide-based resin and a second resin containing a copolymer including polyamide-based segments and polyether-based segments; a co-extruded film including a base film including a first resin layer containing a polyamide-based resin, and a second resin layer containing a copolymer having polyamide-based segments and polyether-based segments; to a co-extruded film including a base film including a first resin layer and a second resin layer, which have different melting points; and to a method for manufacturing a polymer film, the method including a base film forming step including a step of co-extruding a first resin and a second resin, which have different melting points.