This invention provides a magnesium oxide vapor-deposition material advantageously usable for forming a magnesium oxide film useful as a protective film for the dielectric layer of an alternating current type plasma display panel by an electron beam vapor-deposition method. The magnesium oxide vapor-deposition material comprises metal oxide in which the valence of the metallic element(s) is any of 3, 4 and 5 in the range of 0.01 to 6 mol%. Alternatively, the magnesium oxide vapor-deposition material comprises alkaline-earth metal oxide other than magnesium oxide, and metal oxide in which the valence of the metallic element(s) is any of 3, 4 and 5 in such a manner that each content is controlled to >=0.005 mol% expressed in terms of the metallic element contents, and also, the total content is controlled to <=6 mol% expressed in terms of the metallic element contents.