A downlight apparatus includes a fixing bar, a driver box, a light container and a light source. The fixing bar has two elastic units and a central part. The two elastic units are located at two opposite sides of the central part. The two elastic units are deformed so as to pass through a central hole of a fixing plate and then are released to attach to the fixing plate. The fixing plate is fixed to a platform. The driver box includes a driver for converting an external power to a driving current. The light container has a top cover and a lateral wall. The fixing bar is fixed on the top cover protruding toward the central hole of the fixing plate. A bottom side of the driver box is placed on the central part.