FUEL CELL SYSTEM

There is provided a fuel cell system which can perform antifreeze of cooling water easily and efficiently. A fuel cell system of an embodiment includes a fuel cell section, and has: a cooling water circulation system in which cooling water circulates via the fuel cell section; a heat exchange system to perform heat exchange between seawater and the cooling water circulating in the cooling water circulation system; and a control section to control the heat exchange. The control section heats the cooling water by the heat exchange when a temperature regarding the cooling water circulation system is equal to or lower than a first threshold value and a temperature of the seawater used for the heat exchange in the heat exchange system is equal to or higher than a second threshold value which is higher than the first threshold value.