PURPOSE: To prevent a fuel reformation device from being deteriorated in its reformation characteristics without losing the load following capability of a plant and also without enlargement of a steam supply equipment, by providing a fuel reformation device, a fuel cell, a steam flow regulator and the first and second controllers.

CONSTITUTION: A detected flow signal 31 transmitted from a flow detector 30 is input in the second control device 34 comprising a calculator 32 and a comparator 33. Here, the calculator 32 shall find out, through its calculation, a material gas flow set value for satisfying a prescribed steam-carbon ratio in response to the constantly input detected steam flow values and the results of calculation shall be output as the upper limit material gas flow setting signal 35. Subsequently, the comparator 33 receives the upper limit material gas flow setting signal 35 and the target material gas flow signal 26 output from a culculator 25, that is a component of the first control device 23. After comparing the levels of both signals with each other, the value of the smaller flow level is selected and output as an amended terget material gas flow signal 36. The amended target material flow signal 36 is given to a regulator 28, that is a component of the first control device 23.