This invention relates to an iron-sulfur complex that is capable of efficiently catalyzing formation of hydrogen, and a method for producing hydrogen using the complex as a catalyst. The iron-sulfur complex provided herein comprises: a structure of formula (I) wherein the ligands L1 to L3, L5 and L6 and the groups X1 to X3 are each selected from the group consisting of alkyl, alkenyl, alkynyl and aryl that are substituted or unsubstituted, hydroxyl, carbonyl, aldehyde, and so on; L4 is a bridging ligand selected from the group consisting of hydroxyl, carbonyl, and so on; and the symbol “z” means the charge, which is an integer with the range of −3 to +2. X1 and X2 may join together to form a bridging group between the two sulfur atoms. X3 may alternatively be a vacant site.