NOVELTY - A fuel cell generating system comprises first solid oxide fuel cell stack for generating power by electrochemical reaction of hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen and supplying waste heat and steam resulting from the power generation to the reformer; and second solid oxide fuel cell stack for generating power by electrochemical reaction of hydrogen ejected from the oxidizer or converter with oxygen.    USE - For generating power by electrochemical reaction of hydrogen with oxygen.    ADVANTAGE - The fuel cell generating system has reduced energy loss and has improved sending end efficiency and increased sending end output power. The temperature of the fuel cell stack and reformer may be controlled even if the sending end output power of the system varies.    DETAILED DESCRIPTION - A fuel cell generating system comprises reformer (3) for producing a reformed gas (27) containing hydrogen by a steam reforming reaction of a fuel; first solid oxide fuel cell stack (57) for generating power by electrochemical reaction of hydrogen or hydrogen and carbon monoxide in the reformed gas with oxygen and supplying waste heat and steam resulting from the power generation to the reformer; converter (4) for converting carbon monoxide in the reformed gas (38) into carbon dioxide and hydrogen by reaction of the carbon monoxide with steam; oxidizer (5) for converting carbon monoxide ejected from the converter into carbon dioxide by oxidation; and second solid oxide fuel cell stack for generating power by electrochemical reaction of hydrogen ejected from the oxidizer or converter with oxygen.    An INDEPENDENT CLAIM is also included for a method of controlling a fuel cell power generating system comprising determining whether an output power of a first power generator increases or decreases; and decreasing an amount of air supplied to the first power generator when the output power of the first power generator increases, or increasing the amount of the air when the output power of the first power generator decreases.    DESCRIPTION OF DRAWING(S) - The drawing shows a diagram of the fuel cell power generating system.    Reformer (3)    Converter (4)    Oxidizer (5)    Reformed gas (27, 38)    Condenser (39)    Solid oxide fuel cell stack (57)