To execute the settings by each frame by detecting the settings timing in the device which perform the decoding processing of the ciphered music data, because a microcomputer makes it possible to change the settings by each frame as the minimum unit of the music data.

This device is provided with a stream control circuit 108 which holds and controls the cipher frame input, an auxiliary data control circuit 109 which holds and controls the auxiliary data input, a header separation circuit 104 which inputs the cipher frame from the stream control circuit 108 and separates the cipher data and the header, a decoding circuit 105 which decodes the cipher data and generates the decoding data based on the auxiliary data from the auxiliary data control circuit 109, and a header combination circuit 106 which combines the decoding data and the header and generates the decoding frame. The stream control circuit 108 verifies that the decoding circuit 105 inputs the auxiliary data and is ready to decode them, and then outputs the cipher frame.