To ensure start-up while securing the durability of a reforming catalyst by decreasing the temperature of combustion gas of a starting combustor at the time of the start-up of a reformer.

A starting combustor 4 is provided with a combustion chamber 6 provided with a glow lamp 10 and a fuel injection valve 8 to burn the mixed gas rich in fuel, a vaporizing chamber 9 vaporizing the fuel injected from the fuel injection valve 8 by the combustion gas formed in the combustion chamber 6 and a mixing chamber 13 mixing air with this vaporized fuel. The fuel injection valve 8 is constituted into one, and it is mounted at the most upstream part of the starting combustor 4 to distribute and supply the fuel in the quantity that becomes richer than a combustible fuel-air ratio to the combustion chamber 6 and the vaporizing chamber 9. While the fuel-air mixture rich in fuel within the range of a flammability limit is formed and burned in the combustion chamber 6, unburned fuel is vaporized by the combustion gas in the vaporizing chamber 9. After that, the vaporized fuel and the combustion gas are mixed with air at the time when they flow into the mixing chamber 13, and then they are supplied to a reforming catalyst 15.