PURPOSE: To extend the life of the reforming tube by preventing any difference between the internal and the external pressure levels of the reforming tube by installing two safety valve device, which act according to the difference between the pressure level of the combusted exhaust gas and that of the reforming gas, between a reforming gas line and a combusted exhaust gas line.

CONSTITUTION: Electrical energy is generated by introducing compressed air supplied from a turbine 16 and a compressor 17 to the oxidant electrode 12 of a fuel cell 10 and introducing a reformed gas supplied from a reformer 1 including a reforming tube 3 to a fuel electrode 11. In the lines connecting a reformed gas line 9 and a combusted exhaust gas line 15, safety valve devices 26 and 27 are installed. The safety valve device 26 acts when the pressure of the combusted exhaust gas becomes higher than that of the reformed gas by at least a specified level to exhaust the combusted exhaust gas outside the device 26. The safety valve device 27 acts when the pressure of the reformed gas becomes higher than that of the combusted exhaust gas by at least by above specified level. Consequently, it is possible to prevent any breakage of the reforming tube 3 of the reformer 1 by avoiding the occurence of a great difference between the internal and the external pressure levels of the reforming tube 3, thereby improving the reliability of the fuel cell power generation system.