A backlight module includes a chassis, a printed circuit board, a light source, and a light guide plate. The chassis includes a bottom plate and a sidewall. The sidewall is disposed on at least one side of the bottom plate. The sidewall has a recess therein. At least one part of the printed circuit board is located in the recess. The light source is electrically connected to the printed circuit board. The light incident side of the light guide plate is opposite to the light emitting side of the light source.