FUEL CELL SYSTEM

A main object of the present disclosure is to provide a fuel cell system capable of rapidly determining occurrence of a leak. The present disclosure achieves the object by providing a fuel cell system comprising: a fuel cell, a coolant circuit that circulates a cooling liquid to cool the fuel cell, a conductivity meter that measures a conductivity of the cooling liquid, and a determination device that determines a leak of the cooling liquid; wherein the determination device includes: an acquisition unit that acquires a conductivity of the cooling liquid from the conductivity meter, and a determination unit that determines a leak of the cooling liquid based on a fluctuation of the conductivity.