The present invention provides a novel and improved metal-air battery in which a lot of catalyst can be disposed in a triple phase boundary, and further, battery properties can be improved. In the metal-air battery according to the present invention, a catalyst layer of an air electrode of a metal-air battery contains a catalyst element and a carbon material, the carbon material comprises two materials of a carbon material A supporting thereon the catalyst element and a carbon material B not supporting the catalyst element, the catalyst layer comprises an agglomerate X containing the catalyst element, the carbon material A and the carbon material B as main components and an agglomerate Y containing the carbon material B as a main component, and the agglomerate X is a continuum and the agglomerate Y is dispersed in the agglomerate X.