An optical fiber composite insulator includes an insulator body in which a through hole having a substantially radially circular cross section is provided, a plurality of optical fibers passed through the through hole, and an organic insulating material gas-tightly sealing the optical fibers in the through hole, wherein a diameter of the through hole is not more than 13 mm, the optical fibers are located inside a hypothetical circle drawn on any plane orthogonal to an axis of the through hole and having a center coaxial with that of the through hole, the hypothetical circle having a diameter equal to 95% of that of the through hole, and a distance between any optical fibers is set at not less than 0.1 mm.