Disclosed herein is a fuel cell which utilizes the biogenic metabolism to produce a high current density. It generates electric power in such a way that the fuel is decomposed stepwise by a plurality of enzymes and those electrons formed by oxidation are transferred to the electrode. The enzymes work such that the enzyme activity of the enzyme involved in decomposition in the early stage is smaller than the sum of the enzyme activities of the enzymes involved in decomposition in the later stage. In the case where a coenzyme is involved, the enzyme activity of the oxidase that oxidizes the coenzyme is greater than the sum of the enzyme activities of the enzymes involved in the formation of the reductant of the coenzyme, out of the enzymes involved in the stepwise decomposition of the fuel. <IMAGE>
