A backlight module includes a frame (55) including a spring element (556), a light guide plate (56) disposed in the frame including an incident surface (561), and a radiation element (59) being pressed onto the incident surface by the spring element. The spring element presses the radiation elements against the light guide plate, and thereby decreases the distance and angle between the radiation elements and the light guide plate. This improves the brightness and uniformity of the emitting luminance of the backlight module.