PURPOSE: To suppress abnormal discharge and prevent breakage of external tube by providing a current breaker which breaks due to an overcurrent, a current flowing into the starter connected in series and positioning the terminal of starter, to which said breaker is connected, in the vicinity of a conductor.

CONSTITUTION: If the starting rare gas leaks from a luminescent tube 1 and thereby abnormal discharge is going to occur in an external tube 12 such abnormal discharge certainly occurs between the other terminal 8 of the starter 4 and the second conductor 3 because the other terminal 8 of starter 4 is located in the vicinity of the second conductor 3 with the different potential thereto. As a result, a short-circuit current of a stabilizer 11 flows into the current breaker 7 and a metal lead or metal body 10 fuses within several seconds. Thereby, abnormal discharge disappears and thereafter power supply to the starter is suspended by the current breaker 7. Accordingly, the starter 4, subsequently the lamp becomes inoperative. Safety operation of lamp can be thus attained by eliminating abnormal discharge and preventing breakage of external tube based on abnormal discharge in the external tube.