Abstract: A phosphor improved against luminance deterioration with time under vacuum ultraviolet irradiation, a phosphor paste composition, and a vacuum ultraviolet excitation light emitting element high in luminance retaining rate and improved in luminance, are presented. An alkaline earth aluminate phosphor which is a phosphor represented by the formula a(M1-xEux)O.6Al2O3 (wherein M represents at least one alkaline earth metal element selected from the group consisting of Ba, Sr and Ca, and x and a satisfy 0<x<1 and O.9≦a≦1.8, respectively) and which has a wide-band peak over an angle region of diffraction angle (2&thgr;) of from 28° to 31° in powder diffraction X-ray spectrum by CuK&agr;1 characteristics X-ray, and a vacuum ultraviolet excitation light emitting element provided with a fluorescent layer made of the phosphor.