Provided is an air electrode/separator assembly including: a hydroxide ion conductive dense separator; an interface layer containing a hydroxide ion conductive material and an electron conductive material and covering one side of the hydroxide ion conductive dense separator; and an air electrode layer provided on the interface layer and including an outermost catalyst layer composed of a porous current collector and a layered double hydroxide (LDH) covering a surface thereof. The outermost catalyst layer has a porosity of 60% or more.