a method for measuring an eccentricity of an optical disk is provided . the method includes steps of : rotating the optical disk with a spindle motor ; irradiating a light beam emitted from an optical pickup on the optical disk ; detecting the light beam reflected from the optical disk with a detector ; generating tracking error signals ; receiving electronic signals from the spindle motor ; calculating a quantity of tracks traversed by the light beam during determined revolutions of the optical disk based on the tracking error signals and the electronic signals from the spindle motor ; and determining the eccentricity of the optical disk based on the quantity of the tracks .