Two substrates are placed opposite each other to form a hermetically sealed space between them. A metal-made partition wall is placed between the two substrates to partition the hermetically sealed space into unit light emission areas. Through holes 20Aa are formed in a matrix arrangement in a portion 20A of the metallic partition wall 20 opposite a display area portion of the back glass substrate 4. Dummy through holes 20Ba are formed in a portion 20B of the partition wall 20 opposite a non-display area portion of the back glass substrate 4. An insulating layer 20a covers the outer surface of the partition wall 20.