A backlight module comprises a light guide plate and a plurality of light sources. The light guide plate comprises a wedged incident part and a flat effective visual part which is abutted with the wedged incident part, wherein the wedged incident part and the effective visual part have a common bottom surface, the thickness of the wedged incident part is thicker than the thickness of the effective visual part, the wedged incident part is provided with an incident surface which is vertical to the bottom surface and an inclined plane which is opposite to the incident part and is connected with the effective visual part, the effective visual part is provided with an illuminating surface which is opposite to the bottom surface, and a plurality of V-shaped grooves for reducing the leaked light of the inclined plane are formed on the inclined plane. A plurality of light sources are arranged adjacent to the incident surface. The V-shaped grooves are formed on the inclined plane, thus, the incidence angle of a light which reaches the inclined plane is increased, and the leaked light of the inclined plane is reduced or eliminated. The invention further discloses the light guide plate which is used by the backlight module.