A backlight module is disclosed. The backlight module includes a light guide plate, a backlight source, an optical plate, and an optical coating layer. The light guide plate has a light emitting surface and a light incident end. The light incident end is located at an adjacent side of the light emitting surface. The backlight source is disposed corresponding to the light incident end and generates lights emitting to the light incident end. The optical plate is disposed above the light emitting surface. The optical plate includes an extension portion extending disposed above the backlight source. The optical coating layer is formed on a surface of the extension portion.