A fuel cell system of the present invention includes a fixing unit that fixes or releases hydrazine; a releasing liquid supplying unit that supplies a water-based releasing liquid for releasing hydrazine fixed in the fixing unit to the fixing unit; a fuel cell to which hydrazine released in the fixing unit is supplied as fuel; a sensing unit for detecting an amount of hydrazine supplied to the fuel cell; and a detection unit that detects an amount of hydrazine fixed in the fixing unit based on a predetermined theoretical hydrazine supply amount to the fuel cell and a hydrazine supply amount detected by the sensing unit.
