A light-emitting diode backlight module includes a base and a light source disposed on the base. The light source comprises a substrate, a heat sink and an LED chip. The base has a heat conductor. The heat sink of the light source is coupled between the substrate of the light source and the heat conductor of the base. The heat sink has a first part which is adjacent a first side of the substrate and a second part which is adjacent a second side of the substrate. The heat sink is in contact with the heat conductor. The LED chip is disposed on the first part of the heat sink and emits light laterally.