A backlight module including a light source, a light guide plate, a lamp reflector and a frame is provided. The light source is disposed at a first side of the light guide plate, and surrounded by the lamp reflector and the light guide plate. The lamp reflector includes a metal substrate and a reflective material layer, and the metal substrate includes a main body and an extended part. The extended part is connected to the main body and disposed under the light guide plate. The reflective material layer is disposed on the main body, and between the main body and the light source, and the light source is surrounded by the reflective material layer and the light guide plate. The light guide and the lamp reflector are disposed on the frame. The backlight module has a better heat dissipation efficiency and lower manufacturing cost.