The present invention provides a fuel cell system using evaporative cooling that generates electricity by reacting hydrogen as a fuel and air as an oxidant. The system includes a fuel cell stack including a cooling channel provided on a bipolar plate separately from an air channel and a hydrogen channel, an air inlet line connected to an inlet side of the cooling channel of the fuel cell stack, a water injection means provided at the inlet side of the cooling channel to inject water into air introduced to the cooling channel through the air inlet line, and an air compression means provided at the rear of the fuel cell stack and connected to a discharge line coupled to an outlet side of the cooling channel to provide a suction force to the cooling channel and to compress a mixture of air and water vapor sucked from the cooling channel. The present system provides advantages in that the configuration of the fuel cell system is simplified, lightweight, and downsized, and the manufacturing cost is reduced.