An audio apparatus includes an input unit for inputting stereo signals in which multi-channel surround-sound signals are mixed in accordance with a predetermined algorithm and a parameter indicating encoded contents of the algorithm, a surround-sound signal generator for generating left-side surround-sound signals and right-side surround-sound signals by decorrelating left-side signals and right-side signals contained in the stereo signals, and a controller for controlling the decorrelation performed by the surround-sound signal generator based on the parameter.