Provided is a fuel cell system including a plurality of fuel cell stacks, in which with a simple configuration, air retention is unlikely to occur in cooling water and a flow rate of the cooling water to each fuel cell stack can be uniformized. In a fuel cell system including a plurality of fuel cell stacks provided with a coolant flow path through which a coolant flows, the plurality of fuel cell stacks are juxtaposed in a horizontal direction, and include a supply pipeline that distributes and supplies the coolant to the coolant flow path, and a discharge pipeline that collects and discharges the coolant that has flowed through the coolant flow path, and the supply pipeline and the discharge pipeline are provided within a formation range where the coolant flow path is formed in the plurality of fuel cell stacks, in a direction of gravity.