A backlight module includes a back plate, a plurality of lamps, a lamp fixing base, and a diffusion plate. The back plate has a cavity. The lamps are disposed on or above the back plate. The lamp fixing base is disposed on the back plate for fixing the lamps. The lamp fixing base has a supporting portion extending along a direction away from the back plate. An orthogonal projection of the supporting portion on the back plate is within a boundary of the cavity. The diffusion plate is disposed above or over the back plate, and the supporting portion is suitable for supporting the diffusion plate.