A fuel cell stack in which cell units are stacked one on top of another, each of the cell units including: a power generation cell; and a separator defining and forming a flow passage portion, being a flow path of the gas, between the separator and the power generation cell, includes a frame body having an insulating property and arranged between at least one set of the cell units adjacent to each other. The frame body includes: as viewed in a stacking direction, outer peripheral beam portions provided to surround an outer peripheral side of a region in which the power generation cell is arranged; a connection beam portion connecting the outer peripheral beam portions to each other; and sealing beam portions formed along sealing portions at least partially sealing a manifold portion through which the gas is allowed to flow to the separator.