In the step of disposing inorganic fibers in the notch portions of the molded body, in order to suppress the shrinkage cavities and hole cavities that occur when impregnating the metal, the inorganic fibers are arranged around the portions where the through holes are provided, that is, the notch portions of the molded body. As the inorganic fibers, it is preferable to use an inorganic fiber having low reactivity with an aluminum-containing metal, for example, an alumina fiber.

The inorganic fibers are preferably disposed such that the filling ratio of the inorganic fibers in the hole-formation portions is 3-30 vol %. If the filling ratio is at least 3 vol %, then the suppression effects of the occurrence of shrinkage cavities and hole cavities is high, and it is possible to keep the maximum value of the size of shrinkage cavities and hole cavities to at most 1.0 mm². When the filling ratio is at most 30 vol %, then subsequent processing of the through holes becomes easy.

In the step of forming the composited portion and the hole-formation portions by impregnating the molded body and the inorganic fibers with an aluminum-containing metal, so-called forging cast processes and die casting processes can be employed in order to impregnate the molded body with the aluminum-containing metal.