PURPOSE: To eliminate the danger of an electric shock by mounting a luminous tube on a socket section through a connection means so as to freely be attached and detached and operation a high voltage generation circuit by means of an interlock unit with regard to the mounting of a second globe onto a first globe.

CONSTITUTION: A luminous tube 7 is arranged at the inner part of a globe 1 so as to freely be attached and detached for a printed circuit board 6. Since the luminous tube 7 is housed in the globe 1, luminous ununiformity can effectively be reduced by the diffused effect of the globe 1 even when a luminous layer 10 is set to ununiform luminous status. In addition, the globe 1 is comprised so as to freely attach and detach first and second globes 2 and 3 and an interlock unit SW is arranged at the inner part. As a result, even if the second globe 3 is removed from the first globe 2, the operation of a high voltage generation unit 5 is stopped with regard to this. Consequently, an electric shock can fully be prevented.