A low-pressure mercury vapor discharge lamp in which a rare gas and mercury are provided in an outer bulb, which in turn contains therein a plurality of bent inner tubes, each having an opening at an end and an electrode at the other end thereof. A starting probe is provided between the openings in the outer bulb. An operating circuit or starter is connected to the electrodes. Further, a starting probe circuit is connected to the starting probe to apply a high voltage to the starting probe at the time of ignition.