It is intended to provide a fuel cell system more capable of exhibiting effects of downsizing and reduction in weight. The fuel cell system of this invention has a stack 1 and a regenerator 7 that are provided in parallel to an air compressor 3. An air supply passage 13 to which an air discharged from the air compressor 3 is supplied and an air discharge passage 14 for discharging an unreacted air to the downstream are connected to the stack 1. A regeneration air supply passage 22 to which the air discharged from the air compressor 3 is supplied and a regeneration air discharge passage 24 for discharging the air to the downstream are connected to the regenerator 7. A fuel pump 6 has a structure that the fuel pump 6 is rotatively driven by the regenerator 7.
