Molten first and second resins are directed to flow in a two-layer and confluent state along a tubular passage formed between a torpedo and a die structure from the nose tip of the torpedo and then along a divergently expanding path along the conical nose of the torpedo respectively as the outer and inner layers, which are thus rendered into uniform thin layers and then extruded from the die as a two-layer laminated tubular structure. A third molten resin may be similarly rendered into a thin tubular layer by forcing it to flow through another tubular passage formed between another torpedo and the inner wall surface formed by a cavity within the first torpedo and directing this third resin to confluently join the layers of the first and second molten resins on the inner side thereof thereby to produce a three-layer laminated tubular structure.
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