A downlight apparatus includes a light module, connecting arms and a driver box. The connecting arms are fixed to a back cover of the light module. The connecting arm has a guiding top and a lateral stopper for entering a receiver slit of the driver box. The lateral stopper and the guiding top may be made of one metal piece, and the lateral stopper is protruding at a lateral side of the connecting arm so that to fix the connecting arm to the driver box.