A backlight module is provided, including a circuit board, a plurality of light-emitting elements, a frame, and a plurality of first and second light-reflecting portions. The light-emitting elements are disposed on the circuit board and separated from each other. The frame includes a base plate and two lateral plates extended from the base plate, wherein the circuit board is disposed on the base plate. The first and second light-reflecting portions are disposed on at least one of the lateral plates and arranged in a staggered manner. The first light-reflecting portions are closer to the light-emitting elements than the second light-reflecting portions. The reflectivity of the second light-reflecting portions exceeds that of the first light-reflecting portions.