PURPOSE: To surely keep the position of a fluorescent lamp while a smooth mounting of the lamp is carried out in the luminaire wherein a long-sized fluorescent lamp is housed in a substantially transparent cover having a lighting circuit built-in box.

CONSTITUTION: A long-sized fluorescent lamp 1 is housed in a transparent cover 2 having a lighting circuit built-in box 3. At least two guide rails 4 are formed in a protruding manner along the longitudinal direction of the cover 2, on the inner surface of the cover 2. A socket 5 detachably made in the cover 2 is provided with a pin socket 5a to be fitted to an electrode pin 1a at the end of the lamp 1 and a groove fitted to the guide rails 4. A lead wire 6 for conduction is introduced in a lighting circuit built-in box 3 through the inside of the cover 2.