PURPOSE: To prevent inflammable gas from remaining in piping and to prevent non-reacted gas from remaining to continue cell electrode reaction by providing a blower capable of sending air in both normal and reverse direcitons as a recycle blower installed in a recycle line.

CONSTITUTION: A recycle piping 14 connected to a fuel recirculation device is branched at a point 'a' from the outlet of a fuel pole 11A, and a part of fuel discharge gas is returned to a point 'b' at the inlet of the fuel pole 11A via a fuel recirculation bidirectional blower 15. Or, a recycle piping 23 connected to an air recirculation device is banched from the outlet of an oxidizer pole 11B and a part of air discharge gas is returned to the inlet of the oxidizer pole 11B via an air recirculation bi-directional blower 24. Both of these poles 11A, 11B and the recirculation devices contribute to adjustment of hydrogen concentration of the fuel discharge gas and oxygen concentration of the air discharge gas, to regulate the voltage generated in a cell through concentration separating action of a fuel cell and also to reuse the not-reacted gas remaining after cell reaction, so that more reaction gas can be supplied to the cell. Thus, a fuel cell power generation plant can be operated at a higher load so that the effect of increased effeciency thereof can be secured.