A control method of a combustion system for controlling combustion of fuel within a combustor, the combustion system including the combustor having a catalyst for promoting the combustion and a first heater arranged so as to be able to supply heat to the catalyst, including: supplying the fuel and oxidizing gas to the combustor along with providing the heat to the catalyst by the first heater; and deactivating the first heater at a prescribed timing and increasing a flow rate of the fuel greater than that have been set before deactivating the first heater, wherein the prescribed timing is determined as a timing at which a generated heat of the fuel prior to deactivation of the first heater becomes equal to or greater than a heat required for raising a temperature of the fuel having the flow rate after increased up to a light-off temperature of the catalyst.