A fuel cell stack is provided with an outlet side oxygen-containing gas communication hole. First and second oxygen-containing gas flow passage grooves are provided in the direction of the gravity while meandering in the horizontal direction on a surface of a first separator. The second oxygen-containing gas flow passage grooves communicate with the outlet side oxygen-containing gas communication hole via second oxygen-containing gas connecting flow passages. A porous water-absorbing tube, which is used to discharge water to the outside of the fuel cell stack in accordance with the capillary phenomenon and the difference in pressure of air, is provided for the outlet side oxygen-containing gas communication hole.