The present invention relates to an active oxygen developing substance composed of an aluminosilicate obtained by heating hydrogarnet as a precursor substance at 700.degree. C. or higher; an aluminosilicate catalyst supporting cobalt oxide, produced by supporting cobalt oxide on the surface of the aluminosilicate; a method for manufacturing these; and applications of these as oxidation catalysts, solid electrolytes, oxygen occlusion carriers, and so forth.