Phosphor and a plasma display device are provided whose deterioration in brightness of phosphors and a degree of change in chromaticity are alleviated and whose discharge characteristics are improved and that has excellent initial characteristics. Phosphor of the present invention is an alkaline-earth metal aluminate phosphor containing an element M (where M denotes at least one type of element selected from the group consisting of Nb, Ta, W and B). In this phosphor, a concentration of M in the vicinity of a surface of the phosphor particles is higher than the average concentration of M in the phosphor particles as a whole. A plasma display device according to the present invention includes a plasma display panel in which a plurality of discharge cells in one color or in a plurality of colors are arranged and phosphor layers are arranged so as to correspond to the discharge cells in colors and in which light is emitted by exciting the phosphor layers with ultraviolet rays. The phosphor layers include blue phosphor, where the afore-mentioned phosphor is used as the blue phosphor.