A battery performance of a metal-air battery is improved while still maintaining a low environmental burden. A metal-air battery includes an air electrode formed from a co-continuous substance having a three-dimensional network structure in which a plurality of nanostructures are integrated by noncovalent bonds; an anode; and an electrolyte disposed between the air electrode and the anode, in which the electrolyte is a gel electrolyte obtained by gelling an aqueous solution containing an ion conductor with a gelling agent, and the gelling agent is constituted of at least one of a plant-derived polysaccharide, a seaweed-derived polysaccharide, a microbial polysaccharide, an animal-derived polysaccharide, and a group of acetic acid bacteria that produce the polysaccharides.