Fuel cell stack

A fuel cell stack comprising:

• a cell stack in which a plurality of unit cells each including a pair of separators is stacked together;
• and
• a seal sheet configured to seal between the unit cells that are adjacent to each other,
• wherein the pair of separators each include a seal line rib on a seal sheet side of the separator, the seal line rib serving as a seal line with the seal sheet, and
• wherein among two facing separators that are a first facing separator and a second facing separator facing each other while sandwiching the seal sheet between the unit cells that are adjacent to each other,
• the first facing separator that is one of the two facing separators includes a protruding portion on at least one part of the seal line rib,
• the second facing separator that is another one of the two facing separators includes a recessed portion in the seal line rib that is configured to fit the protruding portion;
• and
• the seal sheet has a three-layer structure consisting of a first sealing layer, an intermediate layer, and a second sealing layer.