A porous supporting carbon body of a gas diffusion layer is provided with a larger number of smaller pores at its catalyst layer side and a smaller number of larger pores at the other side, particularly with an appropriate distribution of finer mesh at its catalyst layer side and coarser mesh at the other side. As a result, a high performance polymer electrolyte fuel cell is obtained in which water generated at the catalyst layer is quickly sucked out to the gas diffusion layer, and is evaporated at the gas diffusion layer to be effectively exhausted to outside the fuel cell, so that excessive water can be prevented from retaining in the gas diffusion electrode, with the polymer electrolyte membrane being maintained at an appropriately wet condition.