Abstract: A composite insulator-packing container is made of a single-faced corrugated fiberboard composed of a linerboard and a corrugating medium joined to one surface of the linerboard. The fiberboard is fabricated in a form of a polygonal prism by folding an original single-faced corrugated fiberboard along ruled lines such that the linerboard is located at an outer periphery of said packing container. The ruled lines are orthogonal to flutes of the corrugating medium and are formed such that when the fiberboard is folded along the ruled lines in the form of the polygonal prism, outer peripheries of shade portions formed around a core member of a composite insulator internally touch or are located radially inwardly near inner peripheral sides of the polygonal prism. A method for packing the composite insulator is also disclosed.