FUEL CELL SYSTEM

A fuel cell system (100) includes a hydrogen supply valve (33) that controls a supply of the anode gas into an anode system, a purge valve (36) that discharges an off-gas from the anode system, a pressure detecting unit (34) configured to measure a pressure inside the anode system, and a purge flow rate estimating unit (4) configured to estimate a purge flow rate of the off-gas discharged from the anode system through the purge valve (36) based on a pressure decrease in a purge valve open state and a pressure decrease in a purge valve close state when an anode gas supply into the anode system stops.