To provide a luminaire capable of increasing an illuminating radiation amount and being improved in the workability for attachment/detachment.

The luminaire is provided with an instrument body 2 attached to a ceiling CB, a lamp socket 7 disposed on the instrument body 2 on its one side, and a lamp 10 attached to the instrument body 2 through the lamp socket 7. The lamp socket 7 is attached to the instrument body 2 through fittings 8. A fixed piece 81 of the fittings 8 has a supporting piece 85, substantially perpendicular to the fixed piece 81, uprightly disposed at an end thereof. The supporting piece 85 is located at a portion of a base 102 of the lamp 10 bordering with an arc tube 101 in a state in which the lamp 10 is put in the lamp socket 7, and has a substantially arc notch portion 85b at a portion thereof corresponding to the base 102. The supporting piece 85 has a reflecting face, for reflecting light from the lamp 10, formed on a face thereof on a side of the arc tube 101.