In a plasma display device, a plurality of agglomerated particle groups in which a plurality of crystal particles made of a metal oxide agglomerate are disposed in the periphery of a protective layer thereof. The plasma display device is driven by the following driving method to display images. An initializing period has a first half of the initializing period in which a second electrode is applied with a voltage gradually rising from a first voltage to a second voltage, and a second half of the initializing period in which the second electrode is applied with a voltage gradually falling from a third voltage to a fourth voltage.