A fuel reforming system generates burnt gas by burning fuel and air in a
burner (6) during system startup, and the temperatures of a reforming
reactor (7) and carbon monoxide oxidizer (40) are raised by supplying the
burnt gas to the reforming reactor (7) and carbon monoxide oxidizer (40).
The temperature of the burnt gas produced by the burner (6) is increased
according to the elapsed time from the beginning of the startup
processing.