Abstract: The present invention relates to a membrane-electrode assembly applied to a polymer electrolyte water electrolysis device (or system) that generates hydrogen and oxygen by electrolysis of pure water and to a polymer electrolyte water electrolysis stack comprising same. The present invention can accelerate entry into a hydrogen economy society by optimizing the compositions of an anode catalyst layer and a cathode catalyst layer among constituent elements of the membrane-electrode assembly to minimize the amount of a catalyst in the catalyst layers and reducing the power consumption to lower the production cost of hydrogen.