In order to study of the effect of fading time on the chemical compositions and mechanical properties of spheroidal graphite cast iron, molten iron was inoculated with Mg-Ca-Si-rare earth metal alloy for spherodization of graphite in melt, and this melt was held from inoculated time to 15 minutes for fading time before pouring in mold. The results obtained from this experiment are as follows; (1) The degree of graphite spheroidization decreased from 94.2% to 89.1% with increasing of fading time, (2) The mechanical properties for tensile strength, elongation, impact strength and hardness were slightly changed with increasing of fading time, (3) The tensile strength in repeated impact fatigue test was decreased with increasing the fading time, and matrix structure showed the tendency of the highest tensile strength and hardness at pearlitic structure and the lowest values at ferritic structure.