To provide a fuel cell system which makes it easy to open a cut-off valve when starting a fuel cell.

The fuel cell system (10) includes: a fuel cell (13) to generate electric power by an electrochemical reaction of a fuel gas and an oxidizer gas; an air inlet cut-off valve (40) to supply the oxidizer gas to the fuel cell (13); and an air outlet cut-off valve (60) to exhaust the oxidizer gas exhausted from the fuel cell (13). As an air compressor (14), when starting the fuel cell (13), after firstly making the air outlet cut-off valve (60) in an open state, a driving source of the air inlet cut-off valve (40) carries out opening operation of the air inlet cut-off valve (40).