The utility model discloses a backlight module for a liquid crystal display device and a liquid crystal display device. The backlight module comprises an LED and a backplane, wherein the backlight module also comprises a heatsink plate arranged on the outer of the backplane; and the LED is linked with the heatsink plate in the mode of heat conduction. The utility model, by arranging the LED on an extra heatsink plate which is arranged on the outer of the backplane, dissipates outward the heat emitted by the LED through the heatsink plate, lowers the temperature of the backlight cavity, and protects the optical components. At the same time, because the backplane is not directly used to dissipate heat, the gradient of temperature distribution on the backplane is reduced, thus, the gradient of temperature distribution in the backlight cavity is reduced and stress of the backlight cavity induced by the temperature gradient is also reduced.