PURPOSE: To provide an illumination apparatus for a system ceiling which can perform the positioning of an illumination cover and prevents the illumination cover from dropping due to vibration and the like.

CONSTITUTION: An illumination cover 9 is put into an opening section 12 surrounded by a fitting metal 7 and T-bars 8, hook pins 10 of the illumination cover 9 are inserted into hook holes 5, fixing pins 11 are brought into elastic contact with elastic pieces 6 to excite the illumination cover 9 to the T-bars 8 side, both side sections are mounted on side pieces 8b of the T-bars 8, and the illumination cover 9 is fitted on the lower face side of the opening section 12.