An apparatus for correcting any warping of a light guide plate includes a retaining device and a heating device. The retaining device includes a top pressing plate, a bottom supporting plate and an oil hydraulic cylinder on the top pressing plate. The oil hydraulic cylinder applies a pressing force on the top pressing plate, and the top pressing plate and the bottom supporting plate cooperatively sandwich and retain a light guide plate. The heating device has a coil of wire for surrounding the light guide plate. The coil of wire is configured for heating the light guide plate, the pressure and the heat thereby correcting the warp of the light guide plate. A method for correcting a warp of a light guide plate is also provided.