To allow the light, which is emitted inward, to sufficiently enter with no prevention into a space formed with a straight tube and lateral coupled tube of an arc tube.

A compact low pressure discharge lamp 1 comprises a twisting tubular glass discharge pipe 2 provided with at least four parallel straight tubes 6 and 7. The straight tubes 6 and 7 are arranged to form a polygonal shape. Lateral coupled tubes 8, 10, and 11 are coupled to the ends, or near them, of the straight tubes 6 and 7, forming a single and continuous discharge path which is closed air-tightly. A metal coil spring 14 extending parallel to the straight tubes 6 and 7 is provided at the central part of a cylindrical space 13 which is, being polygonal in cross section, formed by the straight tubes 6 and 7 of the arc tube 2.