A light guide plate includes a body having a bottom surface and a light output surface opposite to the bottom surface. A scattering structure is formed on the bottom surface. The scattering structure includes a number of scattering dots located in the form of a number of concentric shapes around the center. The scattering dots adjacent to the center are arranged in a plurality of concentric circles. The scattering dots adjacent to the edge are arranged in a number of concentric quadrilaterals having a shape substantially corresponding to a shape of the light guide plate. A backlight module using the light guide plate is also provided.