A fuel cell stack in which at least one of a plurality of fuel cell units constituting a fuel cell stack includes a water absorbing member with a surface exposed to the atmosphere in a portion where an oxidizer flow path forming member and a separator are in contact with each other, and an area of a surface exposed to the atmosphere of the water absorbing member of the fuel cell unit the temperature of which becomes relatively lower is larger than an area of a surface exposed to the atmosphere of the water absorbing member of the fuel cell unit the temperature of which becomes relatively higher.