A fuel cell stack includes cell units and separators that are alternately stacked, in which each of the cell units includes a single cell. Each of the separators includes: at least one first ridge that is disposed on a first main surface of each of the separators at a predetermined interval to form at least one first gas channel; and at least one second ridge that is disposed on a second main surface of each of the separators at a predetermined interval to form at least one second gas channel. The at least one first ridge and the at least one second ridge are disposed at a regular interval around a center of each of the separators in a cross section perpendicular to the first or second gas channel. The at least one first ridge and the at least one second ridge of the separators are arranged such that a first ridge and a second ridge of a first separator of two of the separators holding each cell unit at least partly overlap respectively with a second ridge and a first ridge of a second separator of the two of the separators in a stacking direction of the separators across a single cell intervened between the two of the separators.