A decoding device for decoding a bit stream defined by MPEG2 Audio Multichannel is provided. The bit stream including an MPEG1 compatible area and an MPEG2 multichannel extended area, the MPEG1 compatible area including MPEG1 side information. The decoding device includes: MPEG1 decoding means for decoding the MPEG1 compatible area; MC decoding means for decoding the MPEG2 multichannel extended area; and MC header detection means for executing a first processing including locating a position of a header of the MPEG2 multichannel extended area based on the MPEG1 side information and shifting a read position of the bit stream to the position of the header.