FUEL CELL SYSTEM

PROBLEM TO BE SOLVED: To provide a fuel cell system excellent in fuel controllability to a reformer, allowing effective collection of pure water required in the system. SOLUTION: This fuel cell system has a fuel cell 1, a hydrogen supply system 3, 14 for supplying a hydrogen-containing gas to the fuel cell 1, an oxygen supply system 7, 8 for supplying a oxygen-containing gas to the fuel cell 1, a humidifying pure water supply system 2 for supplying humidifying pure water to the fuel cell 1, and a condenser 4. The condenser 4 exchanges heat between exhaust from a negative electrode of the fuel cell 1 and fuel stored in the fuel tank 14 in the hydrogen supply system to condense water contained in the exhaust, and supplies the condensed water to the humidifying pure water supply system 2.