PURPOSE: To make the temperature distribution of a single battery plate homogeneous, and increase the generation efficency of an entire fuel cell by making oxidant flows for two adjacent unit cell plates to be in opposite directions to one another.

CONSTITUTION: Air used as an oxidant, after being introduced into a plenum a 36 from an oxidant supply hole 34 provided in a manifold cover A 31, is introduced into a distribution groove 24 from distribution-groove inlets 25 provided on the side surface of a separating plate A 21, and equally supplied into oxidant supply grooves 23. Next, the air supplied into the grooves 23 reacts with a fuel gas through unit cell plates 2 interposed between the separating plates A 21 and a separating plate B22 to produce steam, comes to have an increased temperature due to the heat of the reaction, and enters into a plenum c38. Then, the air entering the plenum c38 changes its flowing direction in the plenum c38, passes through the oxidant supply grooves 23 of another separting plate, and reaches the distribution groove 24 while continuously undergoing the above reaction. After that, the air reaching the groove 24 is discharged into a plenum b37 from distibution-groove outlets 26, and discharged outside the fuel cell from an oxidant exhaust hole 35.