To precisely position an optical fiber on the outer circumference of a core member in spiral state, lower the fluidizing resistance of an outer coating forming material in an outer coating forming space in molding dies, and produce a composite insulator pipe incorporating an optical fiber without any voids.

In the case an optical fiber built-in-type insulator pipe constituted of a core material 1, an optical fiber 2 spirally wound on the outer circumference of the core material 1, an outer coating formed on the outer circumference of the core material 1 and the optical fiber 2 by this method, a recess spirally extended in the outer circumference of the core material 1 is formed. Then, an insulating polymer material 8 for forming un-cured coating is applied to the outer circumference of the optical fiber 2 and the resultant optical fiber 2, which is coated with the insulating polymer material 8 for forming un-cured coating, is fitted in the recess, the resultant core material bearing the optical fiber 2 is put in molding dies for forming outer coating, and after the molding dies are fastened, the outer coating forming space between the inner faces of the molding dies and the outer surfaces of the recess and the optical fiber 2 is filled with a material for forming an outer coating and then the insulating polymer material 8 is cured to form an outer coating.