PURPOSE: To produce the granulated powder for preform which is not deformed in molten metal casting at the time of producing the granulated powder as the raw material for the preform to produce a fiber-reinforced metal by agitating the raw material utilizing ultrasonic vibration.

CONSTITUTION: A vessel 2 is arranged in an ultrasonic wave generator 1, a small amt. of water 3 and an inorg. binder 4 such as glass powder are introduced into the vessel and mixed, the mixture is agitated by an agitator 5 while imparting ultrasonic vibration, and then a coupling agent 6 such as a silane coupling agent is added and agtiated prepare a preliminary dispersion 7. A reinforcing fiber 12 such as a whisker of aluminum boride is added to a liq. mixture obtained by agitating the water 11 and org. binder 9 such as PVA in another vessel 8 with an agitator 10 and agitated, and the dispersion 7 is added to the agitated liq., agitated and then granulated with a spray drier 15. A preform is formed from the granulated powder, the preform is pressure- impregnated with the molten Al alloy and composited to produce a fiber- reinforced metallic part with the generation of defective products resulting from the deformation of the preform reduced.