The present invention provides a side-edge backlight module, which includes: a backplane (2), a backlight source (4) mounted in the backplane (2), and a light guide plate (6) mounted in the backplane (2). The backlight source (4) includes a circuit board (42), a plurality of LED lights (44) mounted to and electrically connected with the circuit board (42), a plurality of vertical heat dissipation boards (46) mounted to the circuit board (42) and arranged between the LED lights (44), and horizontal heat dissipation boards (48) perpendicularly connected to the vertical heat dissipation boards (46). The horizontal heat dissipation boards (48) are mounted to the backplane (2). By mounting the vertical heat dissipation boards to the circuit board of the backlight source and mounting the horizontal heat dissipation boards to the bottom board of the backplane, with the horizontal heat dissipation boards and the vertical heat dissipation boards being jointed to or engaging with each other, the side-edge backlight module of the present invention effectively enhances the heat dissipation performance. Further, the vertical heat dissipation boards are arranged between adjacent LED lights and are located on the same side of the circuit board as the LED lights so as to further enhance the heat dissipation performance and thereby improving the quality of the side-edge backlight module.