PURPOSE: To eliminate carbonization of a terminal due to arc generation and facilitate lamp replacement by furnishing a sensing switch which lights up an all-night light when mechanical detention of the body of an illuminating fixture with a lamp retainer is disengaged.

CONSTITUTION: When a lamp is held in a lamp retainer 21 and it is fitted in a recess 5 in the body 1 of illuminating fixture, a resilient detent pieces 32 of the retainer 21 is detained mechanically with a detaining hole 6 in the recess 5. The detent piece 32 pushes the actuator 38a of a sensing switch 38 to put off an all-night light which has been lit. If a removal operating piece 33 for the retainer 21 is pushed for replacement of lamps 22, 23, detention with the detaining hole 6 is disengaged, and now the retainer 21 is ready for removal. At this time, pressure on the actuator 38a is disengaged, and the all-night light is illuminated. This eliminates carbonization due to generation of arcs, and facilitates lamp replacement.