A fuel cell stack comprising: at least two cell modules adjacent to each other, the cell modules each being formed by stacking a plurality of fuel cells into an integrated unit; characterized by a seal plate (P1, P2) to be interposed in a cooling flow channel which is defined between separators (40, 41) of the cell modules, the cooling flow channel configured to allow a cooling fluid to flow therethrough, the seal plate (P1, P2) comprising: a conductive metal plate, a manifold portion in which a plurality of manifold holes (M1, M3, M4, M6) are formed to allow two kinds of power-generation gases to flow separately through the manifold holes (M1, M3, M4, M6) and flow in and out through the plurality of fuel cells; a seal member (51, 52, 53, 54) provided along a peripheral portion of each of the manifold holes (M1, M3, M4, M6) to provide sealing for a corresponding one of the power-generation gases flowing through the manifold hole (M1, M3, M4, M6); manifold holes (M2; M5) for the cooling fluid; and a pressure-drop adjustment portion (B1, B2, B3, B4, B5, B6, B7, B8, B9) configured to reduce or adjust a pressure drop of the cooling fluid flowing through the cooling flow channels by reducing or changing the cross section area of each cooling flow channels. at least two cell modules adjacent to each other, the cell modules each being formed by stacking a plurality of fuel cells into an integrated unit; characterized by a seal plate (P1, P2) to be interposed in a cooling flow channel which is defined between separators (40, 41) of the cell modules, the cooling flow channel configured to allow a cooling fluid to flow therethrough, the seal plate (P1, P2) comprising: a conductive metal plate, a manifold portion in which a plurality of manifold holes (M1, M3, M4, M6) are formed to allow two kinds of power-generation gases to flow separately through the manifold holes (M1, M3, M4, M6) and flow in and out through the plurality of fuel cells; a seal member (51, 52, 53, 54) provided along a peripheral portion of each of the manifold holes (M1, M3, M4, M6) to provide sealing for a corresponding one of the power-generation gases flowing through the manifold hole (M1, M3, M4, M6); manifold holes (M2; M5) for the cooling fluid; and a pressure-drop adjustment portion (B1, B2, B3, B4, B5, B6, B7, B8, B9) configured to reduce or adjust a pressure drop of the cooling fluid flowing through the cooling flow channels by reducing or changing the cross section area of each cooling flow channels. a conductive metal plate, a manifold portion in which a plurality of manifold holes (M1, M3, M4, M6) are formed to allow two kinds of power-generation gases to flow separately through the manifold holes (M1, M3, M4, M6) and flow in and out through the plurality of fuel cells; a seal member (51, 52, 53, 54) provided along a peripheral portion of each of the manifold holes (M1, M3, M4, M6) to provide sealing for a corresponding one of the power-generation gases flowing through the manifold hole (M1, M3, M4, M6); manifold holes (M2; M5) for the cooling fluid; and a pressure-drop adjustment portion (B1, B2, B3, B4, B5, B6, B7, B8, B9) configured to reduce or adjust a pressure drop of the cooling fluid flowing through the cooling flow channels by reducing or changing the cross section area of each cooling flow channels.