To improve the productivity by reducing processes and manhours, to lighten a product by thinning, to improve a cast surface and to prevent the development of cast defect.

A stainless steel-made thin parts 4 containing a prescribed quantity of Si and having 1400-1700°C melting temp. is formed with a shell casting method. Since the shell casting method having remarkably less process than a conventional lost wax method is used, the processes and man-hours are remarkably reduced, and the productivity is improved. Further, the generation of gas is reduced because the melting temp. of the stainless steel material is lower than that of the conventional material, and further, since the generated gas is exhausted by passing through the shell mold 1, the cast defect of blow hole, etc., in the product 4 is not developed, and the machinability of the product 4 is improved. Then, the roughening of the cast surface due to the sand of the shell mold 1 melting onto the surface of the product 4 is not developed, because the temp. of the molten metal 2 is low, and the extremely good cast surface is obtd.