A backlight module includes a back plate having at least one side and a backlight unit including an optical plate and an optical film. The at least one side has a surface, and the surface is disposed with a supporting member. The supporting member includes a horizontal portion and a vertical portion extended from the horizontal portion. In addition, the vertical portion includes a plane surface and a protruding piece, and the plane surface is used for supporting the optical plate and the protruding piece is used for positioning the optical film; and a liquid crystal display device has the backlight module.