Disclosed herein is a downlight module that includes a light source driving board, an isolating board, a lens module, a back housing, and an input power line. The light source driving board includes a light-emitting diode and a driving circuit. The isolating board has a through hole. The lens module includes a lens housing, wherein the light source driving board and the isolating board are disposed in the lens housing. The back housing covers the lens housing of the lens module. The back housing has an opening, wherein the melting temperature of the back housing is lower than the melting temperature of the lens housing. The input power line is connected with the light source driving board via the opening of the back housing and the through hole of the isolating board.