To enhance corrosion resistance and prevent the occurrence of corrosion of an optical fiber unit pipe by using a fiber-reinforced plastics pipe composed of chemically stable plastics and fiber as the optical fiber unit pipe.

In the case where a fiber reinforced plastics pipe is used as an optical fiber unit pipe, unsaturated polyester, an epoxy resin, bismaleimide, addition polyimide or a condensed polyimide high heat resistant resin is used as plastics. Glass fiber, carbon fiber, boron fiber, silicon carbide fiber, aramid fiber or whisker and the like is used as the fiber, which is contained at 30-90 vol.% in view of strength. With respect to the combination between the plastics and the fiber, combination between unsaturated polyester and the glass fiber or combination between the epoxy resin and the glass fiber is preferable in view of the mechanical strength. Consequently, it is possible to prevent the occurrence of corrosion and to made if light-weight and enhance strength in comparison with an aluminum pipe or the like.