PURPOSE: To prevent the shadow of a louver from being imaged in a side-wall part surrounding the louver and avoid the state that light from a light source is reflected by the side-wall part.

CONSTITUTION: A side-wall part 7 nearly vertical to a ceiling 1 is disposed in the periphery of the opening part 2 or the recessed part formed in the ceiling 1, and a louver 6 for transmitting light from a light source 5 is disposed at the middle part in the height direction of the side-wall part 7, thereby showing that the ceiling 1 visually looks high. Also, the arrangement of the light source 5 with respect to the lower edge 12 of the side-wall part 7 is determined in relation to the shading angle β of the louver 6, thereby preventing light from the light source 5 which passes through the louver 6 from shining the side-wall part 7.