A backlight module is disposed under a plurality of keyswitches of a lighting keyboard. The backlight module includes a lighting chip and a light guide plate. The lighting chip has a first illumination unit and a second illumination unit arranged side by side. The light guide plate has a hole structure where inside the lighting chip is disposed. A lateral side of the hole structure facing an illumination surface of the lighting chip includes a first area and a second area formed in a non-linear manner, respectively corresponding to the first illumination unit and the second illumination unit. The first area guides a first output beam of the first illumination unit toward the second area. The second area guides a second output beam of the second illumination unit toward the first area.