A metal air battery including: a gas diffusion layer having a first surface and a second surface opposite to the first surface; at least one positive electrode layer disposed on the first surface and the second surface of the gas diffusion layer, wherein the positive electrode layer is configured to use oxygen as an active material and includes a first electrolyte; a second electrolyte disposed on the positive electrode layer; and a negative electrode metal layer disposed on the second electrolyte, wherein a side surface of the gas diffusion layer, which connects the first surface and the second surface of the gas diffusion layer, is exposed to an outside of the metal air battery, and the gas diffusion layer comprises an air flow channel that extends from the side surface of the gas diffusion layer which is exposed to the outside, to an inside of the gas diffusion layer.