A hydrosilylation iron catalyst prepared from a two-electron ligand (L) and a mononuclear, binuclear, or trinuclear complex of iron indicated by formula (1), Fe having bonds with carbon atoms included in X and the total number of Fe-carbon bonds being 2-10. As a result of using iron, the hydrosilylation iron catalyst is advantageous from a cost perspective as well as being easily synthesized. Hydrosilylation reactions can be promoted under mild conditions by using this catalyst. Fe(X)a  (1) (in the formula, each X independently indicates a C2-30 ligand that may include an unsaturated group excluding carbonyl groups (CO groups) and cyclopentadienyl groups, however at least one X includes an unsaturated group, a indicates an integer of 2-4 per Fe atom.)