A phosphor in which water adsorption onto the surface of a blue phosphor is inhibited, luminance degradation and chromaticity shift of the phosphor is decreased, or discharge characteristics thereof is improved, and a plasma display device using the phosphor. In phosphor layers used for plasma display, selectively coating at least the vicinity of the sides of planes of mirror symmetry containing Ba atoms in a blue phosphor with an oxide or a fluorine-containing oxide inhibits water adsorption onto the surface of the blue phosphor, decreases luminance degradation and chromacity shift of a phosphor, or improves discharge characteristics thereof.