A ceiling light apparatus includes a fixing bracket, a main housing and a light source. The fixing bracket is firstly fixed on a ceiling. The fixing bracket has a first end, a main part and a second end. The main housing includes a back cover. The back cover has a first connector and a second connector. When the main housing is to be attached to the fixing bracket, the first end is firstly attached to the first connector and then the first end is rotated with respect to the first connector to move the second end to approach to the second connector for elastically locking the second end to the second connector. The light source is enclosed by the main housing for emitting a light via a light opening of the main housing.