To provide a fuel cell system in which valve-opening control of an electromagnetically driven on-off valve is performed in consideration of temperature characteristics of the electromagnetically driven on-off valve.SOLUTION: A fuel cell system includes a fuel cell, an electromagnetically driven on-off valve, a cooling channel, refrigerant temperature measuring means, energization control means, and outside air temperature measuring means. The energization control means has storage means storing a relationship between a temperature of the electromagnetically driven on-off valve and a valve opening current. The energization control means estimates that an outside air temperature and the temperature of the electromagnetically driven on-off valve are the same, and acquires a valve opening current A at the temperature from the storage means, and also estimates that a refrigerant temperature and the temperature of the electromagnetically driven on-off valve are the same, and acquires a valve opening current B at the temperature from the storage means. When acquired valve opening currents are the same, the energization control means applies the valve opening current to the electromagnetically driven on-off valve while, when acquired valve opening currents are different from each other, applies a larger valve opening current, to the electromagnetically driven on-off valve.SELECTED DRAWING: Figure 2