A fuel cell system comprises a fuel cell, a tank, a 1st pressure sensor that measures a fill-time pressure, a 2nd pressure sensor that measures a supply piping pressure, a temperature sensor that measures an internal temperature of the tank; and a controller that, when the fuel cell starts, derives an estimated pressure value of the supply piping pressure based on a 1st pressure value that shows the fill-time pressure, the internal temperature when the 1st pressure value was measured, and the internal temperature when the supply piping pressure was measured, and that detects as the supply piping pressure the lower value among the estimated pressure value and the 2nd pressure value that shows the measured supply piping pressure.