Abstract: A process for manufacturing an Al—Si alloy for use in a vehicle propeller shaft is provided. The Al—Si alloy manufacturing process includes the steps of heating and melting Al—Si alloy where Si contains 13-40 weight percentage (wt %) of the whole alloy, to thereby prepare melt, maintaining the melt at 700-900° C. and then spraying an high pressure inert gas to the melt and rapidly solidifying the same to thereby obtain a forming body, and extruding the forming body at 400-550° C. The physical properties of the Al—Si alloy manufactured by a spray forming process is at least similar to that of the vehicle propeller shafts which have been already known, and also spotlighted as new alloy compositions which can replace the conventional propeller shaft material.