A fuel cell system includes: a fuel cell; a first valve device provided at an oxidation gas supply channel; a second valve device provided at an oxidation off-gas discharge channel; a third valve device provided at a bypass channel; an abnormality detection unit configured to detect an abnormality; and a control unit. The control unit causes the fuel cell to initiate fail-safe power generation if (i) a different abnormality from a valve opening abnormality is detected in the first valve device, (ii) the different abnormality is detected in the second valve device, or (iii) any abnormality is detected in the third valve device. During the fail-safe power generation, if any abnormality is additionally detected in any valve device different from the valve device in which an abnormality is already detected, the control unit stops power generation by the fuel cell.