Fuel cell stack

A fuel cell stack configured by alternately stacking a membrane electrode structure and a separator in a predetermined direction, wherein

• the membrane electrode structure includes a membrane electrode assembly having an electrolyte membrane and electrodes, and a frame member supporting a peripheral portion of the membrane electrode assembly,
• the separator includes a first plate member having a first surface and a first opposite surface, and a second plate member having a second surface and a second opposite surface facing the first opposite surface, and is configured to form a cooling flow path through which a cooling medium flows between the first opposite surface and the second opposite surface,
• the first plate member and the second plate member are configured in a concave-convex shape so as to form gas flow paths through which a reaction gas flows between the first surface and the membrane electrode structure and between the second surface and the membrane electrode structure, respectively, from a first communication hole on one end side of the separator penetrating the separator to a second communication hole on another end side of the separator penetrating the separator,
• each of the gas flow paths includes a first gas flow path facing the membrane electrode assembly, a second gas flow path extending from the first communication hole toward an inlet of the first gas flow path or from the second communication hole toward an outlet of the first gas flow path, and a third gas flow path between the first gas flow path and the second gas flow path, and
• the third gas flow path includes a plurality of protruding portions protruding from the first surface and the second surface toward the membrane electrode structure, respectively, in a state where the first opposite surface and the second opposite surface are separated from each other.