Fuel cell system, the fuel cell of the valve system, and a fuel gas supply system

A fuel cell system includes a first shut valve capable of shutting off a gas flow in a gas path where a fuel cell gas flows; and a second shut valve arranged more towards the downstream side of the gas flow than the first shut valve, and capable of shutting off the gas flow. In each of the first shut valve and the second shut valve, sealing is performed by intimate contact between a movable member and a seal member and a gas pressure supplied from the upstream applies a force to the movable member to bring it into intimate contact with the seal member. A deformation degree by an external force of the same intensity is set greater in the seal member of the second shut valve than in the seal member of the first shut valve.