PURPOSE: To obtain a film excellent in mechanical performance and in self- reinforcing property by a method wherein liquid crystalline polyester is melted and extruded onto a mandrel so as to be deformed by flowing biaxially and finally to be cooled down.

CONSTITUTION: Polyester, in which nematic liquid crystal is formed at a temperature above its melting or fluidizing temperature and which shows an optical anisotropism in a liquid state, is empolyed as liquid crystalline polyester. When said molten liquid flows down by gravity on the surface of a mandrel by extruding the molten polyester liquid onto the mandrel, the flow of the liquid occurs both in the drop direction and in the direction normal to the drop direction on the basis of the shape of the mandrel. As a result, biaxial molecular orientation is induced in the molten liquid, resulting in allowing to obtain an isotropic film excellent in strength against tear. The preferable running mode is that the biaxial flow deformation is normally set to give an one point five to eight- fold draft in the take-up direction and a two-to ten-fold draft in the direction normal to the take-up direction.