To provide a phosphor having stable address discharge voltage characteristics without deteriorating luminance property in a short-time drive, to provide a plasma tube array type display device in which a phosphor layer using the above phosphor is formed inside a discharge slender tube, and to provide a planar light source.

The phosphor 160 excited by ultraviolet light emitted with gaseous discharge is provided with at least one layer of the protective film 161 for protecting the surface of particles of the phosphor 160, and a fine particle cover layer formed so that the fine particles 162 disperse on and cover the surface of particles of the phosphor 160 or the surface of the protective film 161. In the plasma tube array type display device and the planar light source, the phosphor layer using the phosphor 160 is formed inside a discharge slender tube.