A backlight module includes a laser light source, a light guiding board located at a side of the laser light source, a first lens and a second lens both located at a light path of light beams emitted from the laser light source. The laser light source includes one laser diode or a plurality of laser diodes. The light guiding board includes a light incident face and a light emerging face. The first lens firstly converges and then diverges the light beams emitted from the laser light source. The second lens changes the light beams passed through the first lens to be parallel light beams. The parallel light beams have a larger width than that of the light beams just emitted from the laser light source. The parallel light beams enter the light guiding board via the light incident face of the light guiding board.