Abstract: A nodular graphite cast iron for pistons according to an embodiment contains, in mass %, C: 2.7 to 4.3%, Si: 2.0 to 3.5%, Mn: 0.3 to 0.8%, Mg: 0.02 to 0.10%, Cu: 0.3 to 1.0%, Cr: 0.05 to 0.90%, and Mo: 0.05 to 1.00% with the balance being composed of Fe and inevitable impurities. Then, the C content and the Si content fall within a composition range defined by a line sequentially joining respective points of point A (2.7%, 3.5%), point B (3.2%, 2.0%), point C (4.3%, 2.0%), and point D (3.8%, 3.5%) indicated by (the C content and the Si content) in a graph illustrating the relation between the C content and the Si content.