To efficiently produce a composite stock with a gravity casting while promoting the impregnation by utilizing the reaction heat of particularly, reinforcing material, matrix metal and molten Al or Al alloy in the production of the composite stock.

This method, contains a process for forming a formed body with metallic fiber, whisker or particles as the reinforcing material and fine pieces composed of Ni. Fe, Co, Cr, Mn, Cu, Ag, Si, Mg, Al, Zn, Sn or Ti as the metal and a process for gravity casting while promoting the impregnation into the formed body with generated heat of intermetallic compound by charging the formed body into a mold and pouring the molten Al or Al alloy.