To provide a method of producing spheroidal graphite cast iron which contains fine spheroidal graphite, and has less micro-shrinkage cavities, and to provide cast iron which has high strength and satisfactory facial roughness.

In the spheroidal graphite cast iron comprising 3.0 to 4.0% C, and 1.5 to 3.0% Si, the ratio between a C content and a Si content is controlled to the one in which the difference between a primary crystal temperature and an eutectic temperature is 15°, and the ratio of a S content in the original molten metal before spheroidizing treatment is controlled to 0.02 to 0.07%, and the ratio of the Mg content after spheroidizing treatment is controlled so as to satisfy the residual Mg ≥ the S% in the original molten metal + 0.01%.