A fuel cell system comprising: a fuel cell that includes a fuel electrode to which fuel is supplied and an oxidizer electrode to which oxidizer gas is supplied and that generates electric power using the fuel and the oxidizer gas; a reforming unit configured to generate the fuel from reforming raw material, which is supplied from a supply source (Gs), and water vapor; an evaporating unit configured to generate the water vapor from reforming water; a fuel supply device (llal) configured to supply the fuel to the fuel cell; a combustion unit configured to burn combustible gas led out from the fuel electrode of the fuel cell using the oxidizer gas; an ignition device (36al, 36a2) configured to ignite the combustible gas introduced into the combustion unit to fire up the combustion unit; and a control device configured to control at least the fuel cell, wherein the control device includes: a fuel reference flow rate setting unit configured to set a target flow rate (Qft) of fuel supplied to the fuel cell to a fuel reference flow rate (Qfk) which is a reference flow rate of fuel on the basis of a power generation amount of the fuel cell during a power generation operation of the fuel cell system, a blow-off determination unit configured to determine whether blowing off, by which a combustion state of the combustion unit is dissolved partially or in its entirety, has occurred or not, and a first ignition unit configured to increase the target flow rate (Qft) of the fuel in a stepwise manner by a fuel increase amount (Qfz), which is set on the basis of an air fuel ratio of the reforming raw material, from the fuel reference flow rate (Qfk), which is set by the fuel reference flow rate setting unit, and perform ignition of the combustible gas by the ignition device (36a1, 36a2) in a case where it is determined, by the blow-off determination unit, that the blowing off has occurred, during the power generation operation of the fuel cell system. a fuel cell that includes a fuel electrode to which fuel is supplied and an oxidizer electrode to which oxidizer gas is supplied and that generates electric power using the fuel and the oxidizer gas; a reforming unit configured to generate the fuel from reforming raw material, which is supplied from a supply source (Gs), and water vapor; an evaporating unit configured to generate the water vapor from reforming water; a fuel supply device (llal) configured to supply the fuel to the fuel cell; a combustion unit configured to burn combustible gas led out from the fuel electrode of the fuel cell using the oxidizer gas; an ignition device (36al, 36a2) configured to ignite the combustible gas introduced into the combustion unit to fire up the combustion unit; and a control device configured to control at least the fuel cell, wherein the control device includes: a fuel reference flow rate setting unit configured to set a target flow rate (Qft) of fuel supplied to the fuel cell to a fuel reference flow rate (Qfk) which is a reference flow rate of fuel on the basis of a power generation amount of the fuel cell during a power generation operation of the fuel cell system, a blow-off determination unit configured to determine whether blowing off, by which a combustion state of the combustion unit is dissolved partially or in its entirety, has occurred or not, and a first ignition unit configured to increase the target flow rate (Qft) of the fuel in a stepwise manner by a fuel increase amount (Qfz), which is set on the basis of an air fuel ratio of the reforming raw material, from the fuel reference flow rate (Qfk), which is set by the fuel reference flow rate setting unit, and perform ignition of the combustible gas by the ignition device (36a1, 36a2) in a case where it is determined, by the blow-off determination unit, that the blowing off has occurred, during the power generation operation of the fuel cell system. a fuel reference flow rate setting unit configured to set a target flow rate (Qft) of fuel supplied to the fuel cell to a fuel reference flow rate (Qfk) which is a reference flow rate of fuel on the basis of a power generation amount of the fuel cell during a power generation operation of the fuel cell system, a blow-off determination unit configured to determine whether blowing off, by which a combustion state of the combustion unit is dissolved partially or in its entirety, has occurred or not, and a first ignition unit configured to increase the target flow rate (Qft) of the fuel in a stepwise manner by a fuel increase amount (Qfz), which is set on the basis of an air fuel ratio of the reforming raw material, from the fuel reference flow rate (Qfk), which is set by the fuel reference flow rate setting unit, and perform ignition of the combustible gas by the ignition device (36a1, 36a2) in a case where it is determined, by the blow-off determination unit, that the blowing off has occurred, during the power generation operation of the fuel cell system.