To provide a fuel cell capable of enhancing power generation performance of an electrolyte layer after starting in a short time by efficiently carrying produced water to the upstream side of hydrogen gas even when flow of air in an oxygen supply layer is insufficient.

The hydrogen gas flow directions in a first fuel supply layer 13A and a second fuel supply layer 13B commonly using an oxygen supply layer 14 are set reversely. The first fuel supply layer 3A and the second fuel supply layer 13B complementarily conduct putting in and taking out of water vapor through the oxygen supply layer 14, the dispersion of planar moisture contents in the oxygen supply layer 14 is leveled. Even if a humidifying/water control mechanism is not present, a first membrane electrode assembly 10A and a second membrane electrode assembly 10B are uniformly humidified from the upstream side to the downstream side, build up of output after starting is made quick, and stable output can be obtained for a long time.

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