PURPOSE: To provide a single-layer tubular packaging casing which has excellent elasticity and other properties and is suitable for sausages by molding a polymer mixture comprising a polyamide 6 and a specified arom. copolyamide, biaxially stretching the molding, and thermosetting the stretched molding.

CONSTITUTION: A polyamide 6 (A), an arom. copolyamide (B) comprising units of hexamethylenediamine, terephthalic acid, and isophthalic acid, and an optional additive (C) (e.g. a silicone oil) are mixed together. The mixing ratio is preferably such that 10 to 30 wt.% of the mixture is accounted for by the component (B) with the balance consisting of the component (A). The polymer mixture is then extruded into a tube of a film having a single layer structure. The tube is biaxially stretched and then thermoset to prepare a casing for packaging. The casing has excellent adhesion to sausages and does not cause wrinkling of the sausages.