Disclosed is a backlight module and a liquid crystal display device including the backlight module. The backlight module includes a rear plate, a light guide plate, an optical film, a reflection sheet, and a position transformation mechanism. The position transformation mechanism is used to interchange the positions of the optical film and the reflection sheet, so that the optical film is located at one of a front surface and a back surface of the light guide plate, and the reflection sheet is located at the other one of the front surface and the back surface of the light guide plate. The backlight module broadens the application scope of liquid crystal display devices, thus providing users with more human-oriented services.