A backlight module (100) includes a light guide plate (56), a bottom tray (50) having a spring finger (506), a radiation element (59) disposed adjacent to the light guide plate, and a frame (55) receiving the light guide plate and the radiation element. The light guide plate includes a light incident surface (560), and a side surface (564) opposite to the light incident surface. An ear (566) is formed on the side surface, and the spring finger presses the light guide plate toward the radiation element. A distance between the radiation element and the light incident surface is thereby decreased or even eliminated. This enables the backlight module to provide improved brightness and uniformity of emitting luminance.