To provide long-life, uniform planar light emission without producing noise.

A transparent electrode 24 and a planar electrode 25 are formed on inner surfaces of glass plates 11, 12, respectively, a sealed container 15 is formed by connecting them by a glass spacer 13, a phosphor film 18 is formed on an inner surface of the transparent electrode 24, and a circumferentially extending auxiliary conductor 31 is formed on a peripheral edge of the transparent electrode 24 projecting from the glass spacer 13. A sine-wave power source 34 is connected between the conductor and the electrode 25 to generate discharge and light emission. A dielectric film 35 is formed all over the inner surface of the electrode 25 surrounded by the glass spacer 13. A seal gas is sealed in the interior. Partial pressure of the discharge gas is of the order of 10 Torr.