A spheroidal graphite cast iron article having a thin portion and a thick portion, the number of spheroidal graphite particles having a diameter of 2 .mu.m or more being 600 /mm.sup.2 or more and less than 2000 /mm.sup.2 in the thin portion and 130 /mm.sup.2 or more and less than 600 /mm.sup.2 in the thick portion, and spheroidization percentage being 70% or more in the thick portion, is produced by a method comprising the steps of: (a) preparing an iron-base alloy melt having a composition consisting essentially by weight of 3.0-4.0% of C, 0.8-1.7% of Si, 1.0% or less of Mn, 0.2% or less of P, 0.01-0.2% of S, the balance being substantially Fe and inevitable impurities; (b) desulfurizing the iron-base alloy melt to control the sulfur content of the melt to less that 0.01% by weight; (c) adding a sulfur-containing material to the melt in such an amount that the sulfur content of the melt becomes 0.011-0.03% by weight; and (d) adding an Mg-containing material and a lanthanide element to the melt to conduct a spheroidizing treatment.