A sound enhancement apparatus and method which produce low IMD over a broadband frequency region and performs BSE to offer a sound which is natural to the human ears, are provided. The sound enhancement apparatus includes a preprocessor, a BSE signal generator, and a gain controller. The preprocessor divides a source signal into a high-frequency signal and a low-frequency signal and analyzes the low-frequency signal to obtain prediction information regarding a degree of distortion that will be generated by the low-frequency signal. The BSE signal generator generates a higher harmonic signal for the low-frequency signal as a BSE signal to be substituted for the low-frequency signal, wherein the order of the higher harmonic signal is adjusted based on the prediction information regarding the degree of distortion. The gain controller adjusts a synthesis ratio of the low-frequency signal and the BSE signal adaptively depending on the prediction information regarding the degree of distortion.