PURPOSE: To form a hollow part having complicate shape even in the case of casting into a lost foam pattern by supporting the end part of a metallic pipe forming a hollow part shape in a finish product with this inner surface by non-bonding sand.

CONSTITUTION: The end part 12a of the metallic pipe 12 forming the necessary shape in the finish product with the inner surface is projected from a foam forming body 13 and supported by the non-bonding sand 28. At the time of pouring molten metal into a sprue 24, a runner 25 and pattern 22 made of the foam forming material are thermally decomposed and lost to fill up the molten metal. As the non-bonding sand 28 is filled up in the metallic pipe 12, the metallic pipe 12 can form the hollow part at the accurate position without breaking and deforming.