A metal air battery includes at least one gas diffusion layer assembly; a positive electrode layer disposed on a surface of the at least one gas diffusion layer assembly, wherein the positive electrode layer is capable of using oxygen as an active material; a protective electrolyte membrane disposed on the positive electrode layer; and a negative electrode metal layer disposed on the protective electrolyte membrane, wherein the gas diffusion layer assembly includes a first gas diffusion layer and a second gas diffusion layer, wherein the second gas diffusion layer is disposed on a first surface and an opposite second surface of the first gas diffusion layer, and wherein a gas diffusivity of the first gas diffusion layer is greater than a gas diffusivity of the second gas diffusion layer. Also, the gas diffusion layer assembly described above, and a method of manufacturing a metal air battery including the gas diffusion layer assembly.