This review describes that the synthetic 4Fe-4S cluster, which is a model compound for an active center of ferredoxin in biological systems, exhibits a prominent function as an electron-transfer carrier or an active site in various chemical oxidation-reduction reactions. The designed reactions using the synthetic 4Fe-4S cluster are as follows : the reduction of acridinium salt, α-diketone, and m-dinitrobenzene with benzenethiol, the reductive cleavage of α-isobutylthiodeoxy-benzoin with 1-benzyl-1, 4-dihydronicotinamide, the reduction of aromatic ketones, aldehydes, esters, and protons with carbanions such as n-butyllithium and phenyllithium, and the activation of hydrogen and the hydrogenation of olefins with the phenyllithium/4Fe-4S cluster system. Furthermore, the function of thiamine coenzyme in pyruvate oxygenase is mimiced and applied to the reduction of 4Fe-4S cluster using thiazolium salt as a model compound.