To propose a technique for a scavenging method to prevent freezing of a fuel cell system.SOLUTION: A fuel cell system includes: a fuel cell; a target component provided in a flow path of reaction gas supplied to the fuel cell; a plurality of temperature acquisition units that acquire temperatures of a plurality of reference components that are different from the target component; and a control unit that controls the fuel cell system. The control unit executes scavenging processing of estimating a plurality of estimated outside air temperatures by using the temperatures of the plurality of reference components acquired by the plurality of temperature acquisition units, estimating the estimated minimum temperature of the target component by using the lowest estimated outside air temperature among the plurality of estimated outside air temperatures, and discharging water from the flow path of reaction gas when the estimated minimum temperature of the target component is predicted to be a predetermined temperature or lower after the operation of the fuel cell system is stopped.SELECTED DRAWING: Figure 2