NOVELTY - The stack (10) has a positioning unit (66) that is provided in a unit performing positioning in an electric power generation unit (12). A positioning unit (68) is provided between the units performing positioning between the electric power generation units. The positioning unit in unit and positioning unit between units are coaxially set with respect to a central axis extended in a lamination direction so as to be adjoined and provided in a fuel gas communicating hole side with respect to between the fuel gas and oxidizing agent gas communicating holes (28a,28b,30a,30b).    USE - Fuel cell stack mounted in fuel cell vehicle.    ADVANTAGE - The positioning unit in a unit performing the positioning in electric power generation unit, and the positioning unit between units performing positioning between electric power generation units are coaxially set with respect to a central axis extended in a lamination direction so as to be adjoined and provided in a fuel gas communicating hole side with respect to between the fuel gas and oxidizing agent gas communicating holes so that the two types of positioning structures are concentrated to compactize the whole fuel cell stack favorably and the displacement of fuel gas communicating hole is regulated when external load is provided to fuel cell stack. Thus, the seal difference of the fuel gas communicating holes is suppressed effectively. Since the cross-sectional area in the fuel gas communicating hole compared with that of the oxidizing agent gas communicating hole is set small, the positioning portion in unit and the positioning portions between units are arranged to adjoin to fuel gas communicating hole. Thus, the inplane space efficiency of separator is improved while favorably reducing the size of separator.    DESCRIPTION OF DRAWING(S) - The drawing shows a exploded perspective view of the electric power generation unit with the fuel cell stack. (Drawing includes non-English language text)    Fuel cell stack (10)    Electric power generation unit (12)    Oxidizing agent gas inlet communicating hole (28a)    Oxidizing agent gas outlet communicating hole (28b)    Fuel gas inlet communicating hole (30a)    Fuel gas exit communicating hole (30b)    Positioning units (66,68)