Hydrogen generating apparatus and fuel cell system

A fuel cell system comprising:

• a reformer that carries out steam reforming of fuel and generates reformed gas containing hydrogen;
• a combustor that heats the reformer, the reformer being arranged on a flame forming side of the combustor;
• an exhaust gas path which covers surroundings of an outer wall of the reformer and through which combustion exhaust gas from the combustor flows;
• a reformed gas path through which the reformed gas sent from the reformer toward the combustor flows;
• an evaporator that generates steam through heat exchange with the combustion exhaust gas, the steam being used to carry out the steam reforming of the fuel in the reformer;
• an air heat exchanger that includes a cylindrical air supply path arranged around the exhaust gas path, and that performs heat exchange between air flowing in the air supply path and the combustion exhaust gas flowing in the exhaust gas path;
• and
• a fuel cell that generates electric power by employing the air from the air supply path and the reformed gas from the reformed gas path,
• wherein the exhaust gas path is configured such that the combustion exhaust gas flows upward from the combustor and the reformed gas path extends downward towards the combustor and passes through the combustor, a gas flow inside the reformer in a portion thereof where the gas flow contacts an outer wall of the reformer is opposed to a flow of the combustion exhaust gas in the exhaust gas path in a portion thereof where the combustion exhaust gas contacts the outer wall of the reformer, and the combustor burns the reformed gas and the air, which have not contributed to a power generating reaction in the fuel cell.