Abstract: A fuel cell system includes: a reformer which generates a reformed gas containing hydrogen by reacting hydrocarbon and moisture with each other; a fuel cell stack which generates electric energy through electrochemical reaction of the reformed gas and an oxidant; an ejector which, using steam as a drive fluid, sucks either a raw fuel containing the hydrocarbon or a recycled gas recovered from an anode exhaust gas, and supplies a resultant gas to the reformer; and a vaporizer which generates the steam by vaporizing water, wherein an operation temperature of the fuel cell stack is higher than a boiling point of water at an operation pressure, and the vaporizer generates the steam through heat exchange with the anode exhaust gas.