A plasma display device, characterized in that a blue phosphor in the phosphor layer thereof comprises a phosphor having a crystal structure of MeMgSi2O6:Eu or Me3MgSi2O8:Eu, wherein Me represents one or more of Ca, Sr and Ba, which is prepared by the use of a precursor synthesized by any of an aqueous solution synthesis, a spray synthesis and a hydrothermal synthesis, and the blue phosphor has an average particle diameter of 0.1 to 3.0 mum. The plasma display device exhibits high luminance and is reduced in the deterioration of luminance during the driving of the panel thereof.