To improve luminous efficiency and to increase luminance without increasing gas pressure or without enlarging a device by making an electric discharge between electrodes provided at both ends of a tube main body filled with gas, providing an insulator in the tube main body, and inclining the flow of electrons in the tube length direction at the time of the discharge.

Opening sections 1a, 1b at both ends of a glass tube 1 are sealed by a (-) electrode 2 and a (+) electrode 3, and a strip piece 1c made of an insulator is arranged in it. The strip piece 1c is twisted by about 180° in the peripheral direction of the tube 1, only one long side is integrally connected to the inner face of the tube 1, and a direct flow section 1e extended in the longitudinal direction is formed on the other long side. A transparent conductive (Nesa) coating 1d for a trigger is formed on the surface of the tube 1 along the direct flow section 1e to easily apply a stable trigger. Xe is filled in the tube 1, a high voltage is applied between both electrodes 2, 3, a trigger is applied to the Nesa coating 1d to cause an electric discharge, and electrons collide with Xe molecules to luminesce.