The present invention provides a solid polymer electrolyte fuel cell comprising a fuel cell stack 21 formed by laminating a plurality of fuel cell units each of which includes a fuel electrode 23, an oxidant electrode 24, and a solid polymer electrolyte membrane 22 interposed between the fuel and oxidant electrodes. The fuel cell unit is operable to generate an electric power through an electrochemical reaction between a first gas supplied to the side of the fuel electrode 23 and a second gas supplied to the side of the oxidant electrode 24. In this fuel cell, the first gas supplied to the side of the fuel electrode 23 and the second gas supplied to the side of the oxidant electrode 24 are adapted to flow generally in opposite directions in the fuel cell stack 21, so that a water created on the side of oxidant electrode 24 is reciprocally moved between the fuel electrode 23 and the oxidant electrode 24 to increase a water holding region in the solid polymer electrolyte membrane 22. The fuel cell of the present invention can improve fuel cell characteristics without providing any humidifier.