The method involves guiding film web directly afterwards in melt form to cooling roller arrangement. The film web is guided around cooling or smoothing roller at circumferential speed higher than the extrusion speed, so that film web is subjected to longitudinal stretching, and is subsequently guided out from cooling roller arrangement, and is then subjected to transverse stretching. Both stretching steps are carried out on the layer in the melt form, so that stretching takes place on both occasions in the form of drawing of melt. The plastic in a layer of film web is extruded from wide-slit nozzle (2) in extrusion direction and subsequently led away over casting roller (3). The tensile forces transversely to the extrusion direction are exerted on the film web to stretch the film web longitudinally and transversely. A film form is established during cooling of layer below melting range. The melt form is established during heating of layer above melting range. The film web is initially extruded in melt form at
