PURPOSE: To shorten lengths of a molding line of a composite element and a curing furnace and to further eliminate variations in a section and a surface shape by providing a resin mortar layer between an inner layer and an outer layer formed of fiber-reinforced resin.

CONSTITUTION: When a cylindrical die 7 is formed around a mandrel 1, only resin 21 for forming an inner layer of a composite tube is supplied to an outer periphery of the die 7. A bandlike fiber mat 22 for reinforcing the resin 21 is wound on the supplied resin as fiber-reinforced resin. Then, resin mortar 30 for forming an intermediate layer is supplied to the fiber-reinforced resin as an inner layer. Thereafter, the resin 21 for forming an outer layer is supplied to the mortar 30 to become the intermediate layer, and a bandlike fiber mat 22 for reinforcing the resin 21 is wound on the resin 21. Thus, a composite element 9 is formed.