PURPOSE: To prevent the development of damage in a product FRM by holding whole of a fiber formed body in metal-made or ceramic-made porous vessel.

CONSTITUTION: In order to perfectly impregnate molten metal 5 into gap in a preform 6 made of fine reinforcing fiber, the molten metal 5 is required to be pressurized with the prescribed high pressure. Then, in order to relieve shock of the preform 6 at the time of pressurizing the molten metal, the preform 6 is held in the metal or ceramic-made porous vessel 8. As the result, crack and deformation of the preform 6 developed at the time of impregnating molten metal under the high pressure can be prevented, and the nondefective product is obtd.