To reduce a working time by casting with using a core to hollow an inside and piercing a casting at a state a core remains in the inside after casting with a laser beam or an electron beam to eliminate filling/removing work of a damage prevention material of wax, etc.

When piercing a turbine blade, a core 11 is inserted in a mold 10 for hollowing an inside of the turbine blade and is cast. Weir cutting off is conducted after casting, while the core 11 remains, successively, piercing is conducted on a blade surface by a laser beam 4 or an electron beam. Next, the core is melted/removed. Accordingly, when piercing is conducted to a casting at a state the core 11 remains in the inside after casting, the laser beam 4 passing an opening 16 pierced is absorbed in a ceramic of the core 11 and is not reaches a facing face, thus, damage of a facing face is prevented. Because the core 9 is melted/removed after piercing, filling and removing works of wax are eliminated.