FUEL CELL SYSTEM

A fuel cell system includes a fuel cell stack, a compressor, an air supply passage, a bypass passage, a bypass valve, an opening degree sensor, and a controller. The air supply passage guides the air discharged from the compressor to the fuel cell stack. The bypass passage branches from an intermediate point of the air supply passage to guide the air discharged from the compressor to a discharge passage without passing through the fuel cell stack. The bypass valve is provided in the bypass passage, the bypass valve being configured to open when an upstream pressure of the bypass valve exceeds a set pressure. The controller estimates a pressure of the air supply passage based on an opening degree of the bypass valve.