A fuel cell system includes: a pressure control valve that is disposed in a supply path for supplying hydrogen and decompresses hydrogen to be supplied to a fuel cell stack; an expander that is disposed upstream from the pressure control valve in the supply path and decompresses and expands hydrogen supplied from a hydrogen tank; a second control valve that is disposed upstream from the expander in the supply path and is able to be switched to one of an open state in which hydrogen is supplied to the expander and a closed state in which a supply of hydrogen to the expander is intercepted or an amount of hydrogen supplied to the expander is less than that in the open state; and a control device including a control unit that controls the second control valve.