NOVELTY - The stack (10) has a reactive-gas flow path formed with reactive-gas entrance communicating hole and a reactive-gas exit communicating hole and for distributing reactive gas in a separator along a separator surface. An entrance and exit buffer part (32a) is provided in an entrance side and an exit side of the reactive-gas flow path and provided with connection flow paths. A depth change part (40) is provided in the reactive-gas flow path and the connection flow path of the buffer part in which flow-path depth is partially reduced toward flow direction of the reactive gas.    USE - Polymer electrolyte type fuel cell stack for use in a vehicle.    ADVANTAGE - The depth change part is provided in the reactive-gas flow path and the connection flow path of the buffer part in which the flow-path depth is partially reduced toward the flow direction of the reactive gas, so that generated water and dew condensation water can be favorably discharged in the flow path by increase/decrease in pressure loss, thus achieving improvement of waste-water property in an easier manner and ensuring desired electric power generation performance by simple and compact structure.    DETAILED DESCRIPTION - The reactive-gas flow path is an oxidizing agent gas flow path (30). The reactive-gas entrance communicating hole is an oxidizing agent gas inlet communicating hole (18a). The reactive-gas exit communicating hole is a fuel gas exit communicating hole (20b). The separator is a cathode side separator (14) and an anode side separator (16). The reactive gas is oxidizing agent gas i.e. oxygen-containing gas.    DESCRIPTION OF DRAWING(S) - The drawing shows an exploded perspective view of a polymer electrolyte type fuel cell stack.'(Drawing includes non-English language text)'    Polymer electrolyte type fuel cell stack (10)    Cathode side separator (14)    Anode side separator (16)    Oxidizing agent gas inlet communicating hole (18a)    Fuel gas exit communicating hole (20b)    Oxidizing agent gas flow path (30)    Entrance and exit buffer part (32a, 32b)    Depth change part (40)