Abstract: A bottom lighting type backlight module includes a frame, a plurality of light sources, a reflecting sheet and one optical sheet. The frame includes a base and a plurality of sidewalls extending from the peripheral of the base to define an opening. The base defines a plurality of guide holes therein. The optical sheet is disposed on the opening of the frame. The optical sheet and the frame collectively define a chamber. The reflecting sheet is supported by the sidewalls, for partitioning the chamber into an illumination space and a heat dissipation space. The reflecting sheet defines a plurality of through holes therein. The light sources are arranged on the base of the frame under the reflecting sheet according to the through holes, illuminating light through the through holes towards the optical sheet. The present backlight module has a thin body with good heat dissipation capability.