FUEL CELL SYSTEM

An object of the invention is to provide a fuel cell system capable of performing a stable start-up operation with stable combustion in a burner unit. At the star-up operation of the fuel cell system, an amount of combustion air delivered to a burner unit 12 by an air blower is adjusted according to a total amount of a raw gas supplied from a raw gas supply device 6 to the burner unit 12 and an estimated amount of a raw gas of raw gas components adsorbed to catalysts in a fuel processor 3 and desorbed and supplied to the burner unit 12 due to a temperatures rise of the catalysts.