A light-shielding strip, for preventing a sealing member from deterioration due to ultraviolet rays, is made of a ultraviolet-shielding material having a resilient plate shape, and comprises: a main light-shielding portion having a length according to at least a circumferential length of an inner periphery of a lamp-protective tube; and first and second overlap portions extending from respective ones of both ends of the main light-shielding portion in a longitudinal direction with each forming a non-parallel convergence shape. The light-shielding strip, rolled in the longitudinal direction, is disposed in the lamp-protective tube to closely fit to the inner periphery of the lamp-protective tube and positioned to oppose to the sealing member. Repulsive force against bending force around an end portion of the light-shielding strip can be dispersed due to the non-parallel convergence shape of the overlap portions, so that a possible-raised portion around the end portion can be suppressed.