A fuel cell system includes: a fuel cell; a fuel gas supply path supplying the fuel gas to the fuel cell; a recycling path returning discharged anode off-gas to an entrance of the fuel cell; an anode off-gas discharge path branching from the recycling path and discharging the anode off-gas to an outside; a first valve in the anode off-gas discharge path; a pressurizer pressurizing the anode off-gas; and a controller performing control to cause the pressurizer to act in at least one of a timing in execution of a purge action supplying the fuel gas from the fuel gas supply path and discharging the anode off-gas to the outside in a first valve open state and a timing in prescribed time after the purge action and assessing abnormality based on a pressure of the recycling path or anode off-gas discharge path or an action amount of the pressurizer.