PURPOSE: To improve battery performance and simplify a construction by flowing in specified direction the first reaction gas through internal manifold, and the second reaction gas and cooling gas through the first and second external manifold respectively.

CONSTITUTION: In a battery stack 1, a fuel gas is supplied to inlet pipes 32 and 33 through the center room of a distributing pipe 16 and an internal manifold system 31. The gas flows through a path 20 to react electrochemically. Exhaust gas of reaction flows through one or both of outer pipes 34 and 35, and is sent outside the stack 1 from a collecting plate 15. An oxidizing gas flows in opposite direction to the fuel gas through a path 21 from an inlet manifoled 42 to react electrochemically. Its exhaust gas is exhausted from a common outlet manifold 42. Heat generated by electrochemical reaction is removed by a cooling gas which is supplied to a path 23 from a common inlet manifold 43. The cooling gas is exhausted through a common outlet manifold 44.