PURPOSE: To compose in such a way as to disable a lamp supporter of a festoon decoration lighting system comprising plural lamp supporter mounting body connected to a series of electric cables separately at required intervals, from being detached.

CONSTITUTION: Each lamp supporter is composed of a pin 33 projecting from a base part 30 so as to penetrate the base part 30 and a conductor of an electric cable, a cylindrical enclosure 31 extending from the base part 30 of the lamp supporter on one side of the cable, and a lid 34 for covering the base part 30 of the lamp supporter on the other side of the cable. The enclosure 31 and the lid 34 have blocking means capable of internal engaging having tooth-shaped projection parts 35, and hereby the enclosure 31 becomes lockable with the inside by a snapping motion of the enclosure 31, in the case of pressurizing from the both sides of the enclosure 31 and the lid 34 so as to clamp the cable. The lamp supporter is also composed of a fixing ring installed so as to cover the projection parts 35 and the teeth 36 of the projection parts 35 on the lower part of the ring, in order to prevent the lid 34 from uncoupling suddenly from the enclosure 31 by holding the projection parts 35 toward the inside.