NOVELTY - A fuel cell system comprises fuel cells which discharge residual fuel gas and comprised by fuel cell aggregate, fuel gas flow channel provided inside fuel cells, modifier which contains modification catalyst which modifies reformed gas into fuel gas, gas holder which supplies fuel gas supplied from modifier to fuel cells, ignition part which induces combustion in combustion part, combustion part which burns remaining fuel gas which did not contribute to power generation reaction, and control part which controls oxidizing agent gas supply section based.    USE - A fuel cell system.    ADVANTAGE - The fuel cell system can stabilize combustion state of combustion part.    DETAILED DESCRIPTION - A fuel cell system comprises fuel cells which discharge residual fuel gas and comprised by fuel cell aggregate, fuel gas flow channel provided inside fuel cells, modifier which contains modification catalyst positioned at the upper part of fuel cell aggregate and modifies reformed gas into fuel gas, gas holder which supplies fuel gas supplied from modifier to fuel cells, ignition part which induces combustion in combustion part, combustion part which burns remaining fuel gas which did not contribute to power generation reaction and oxidizing agent gas which is mixed with upper part of fuel cells, temperature acquisition part which acquires temperature of combustion part directly or indirectly, oxidizing agent gas supply section which supplies oxidizing agent gas used for modifier at modification of reformed gas, and control part which controls oxidizing agent gas supply section based on temperature of combustion part acquired by temperature acquisition part. The partial oxidation reforming reaction is performed in modifier when combustion in combustion part starts by action of ignition part. The supply amount of oxidizing agent gas supplied to modifier when temperature of combustion part acquired by temperature acquisition part acquired is less than reference temperature control part. The oxidizing agent gas supply section is controlled to become less than supply amount of oxidizing agent gas supplied to modifier when temperature of combustion part acquired by temperature acquisition part turns into more than reference temperature.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of fuel cell module.    Base component (2)    Exhaust port (11)    Board (15)    Supporting component (15a)    Exhaust gas chamber (17)