To more promote the lightening of a casting having a cavity part.

An automobile knuckle 1 is molded as a casting, and a hollow member 5 is internally insert-cast in the strut fitting arm 3 thereof. The hollow member 5 has a closed space 5a formed by crushing both the edge parts of a pipe material 6 and closing the same, and is cast by inserting projection parts 5b, 5c for positioning formed by the crushing into the respective cores 23, 24 molding the respective internal peripheral faces between an axle supporting part 2 and a strut fixing part 3a and placing the same on a mold. A cavity part can be formed at the casting by the internally insert-cast hollow member, and there is no need of performing exhaust treatment to the hollow member like cores, thus there is no need of receiving limitation on the material of the hollow member, and the further lightening of a cast component is made attainable.