To correspond to downsizing of a lid.

A fuel cell system is equipped with a hydrogen tank 100 stocking hydrogen gas, a supply inlet 200 supplying the hydrogen gas to the hydrogen tank, the lid 220 covering an outside of the supply inlet, a pipe 300 connecting the hydrogen tank to the supply inlet, a pressure sensor 320 arranged in the pipe, a communication device 700 to communicate with a hydrogen supplying device outside, and a control part 400 adjusting a quantity of supply of hydrogen to the hydrogen tank by performing communication with the hydrogen supplying device. When a hydrogen pressure detected by the pressure sensor changes its value by more than a predetermined value during supply of the hydrogen gas, the control part begins to communicate with the hydrogen supplying device 80.