The invention provides a backlight module and a liquid crystal display device. The part which is provided with an adhesive tape (3) is adhered to the outer surface of a side plate (103) of a backboard (10), and the other part of the adhesive tape (3) bends outward from the top end of the side plate (103) and adheres to a liquid crystal panel (2), so that the liquid crystal panel (2) and the backboard (10) are fixed. On the premise that narrow frame of the liquid crystal display device is realized not by using an adhesive frame and square glue, problems of glue leakage and degumming in an assembling process of the backlight module and the liquid crystal panel.