A fuel cell stack includes a first separator and a second separator that are adhered to face each other between adjacent membrane electrode assemblies (MEAs) and each have a plurality of manifolds, a reacting region, and a guide region disposed between the plurality of manifolds and the reacting region. In the fuel cell stack, a first cooling medium guide channel guiding flow of a cooling medium between the plurality of manifolds and the reacting region is formed in the guide region of the first separator; a second cooling medium guide channel guiding flow of the cooling medium between the plurality of manifolds and the reacting region is formed in the guide region of the second separator; and at least portions of the first cooling medium guide channel and the second cooling medium guide channel overlap to communicate with each other.