PURPOSE: To improve the occurrence of poor products and to enhance productivity, by spirally winding thermoplastic resin extruded in a plate shape on a rotating mandrel and coating thermosetting resin impregnated fiber thereon.

CONSTITUTION: The thermoplastic resin plate 3 is continuously extruded from an extruder 2 and spirally wound around a rotating mandrel 1. The winding is performed so that parts of the edges in the width direction of the plate 3 are overlapped or butted, and they are melted and bonded by using a welder 4. The plate is taken off by a take off machine 5 and pipe 17a which is to become a core material is obtained. Glass fiber 6, in which the thermosetting resin is impregnated in a resin impregnating tank 7, is coated on the pipe. The pipe is introduced into a hardening booth 12, wherein the thermosetting resin is hardened and a reinforced plastic layer 17b is formed. A sealing material 14 of the thermoplastic resin plate is extruded and wound around the layer 17b, so that the parts are overlapped, melted and bonded so as to form an external skin layer by a welder 15. Thus the compound pipe 17 is obtained.