An audio coding apparatus includes an audio coding unit 101 for, when it has received an audio signal input, performing coding to the audio signal input and outputting coded audio data and coding related data which is data relating to the coding, as specific data, an ancillary audio coding unit 102 for, when it has received an ancillary audio signal, performing coding to the ancillary audio signal and outputting coded ancillary audio data, and an auxiliary data output unit 103 for producing, from the specific data and the coded auxiliary data, auxiliary data including both of the specific data and the coded ancillary audio data, and outputting the auxiliary data.