PURPOSE: To improve a 'level' that the increase of sub information exceeds the compressibility of main information and to further improve the compressibility of the entire output signal string.

CONSTITUTION: This acoustic signal encoding device for converting acoustic signals 1 to the digital code information of high quality and outputting it as encoded data is provided with a band divider 2 for dividing the acoustic signal 1 into plural frequency components, an adaptive sub information encoder 41 for encoding a scale factor obtained from the output of the band divider 2 and noise allocation information obtained from an auditory model 4, generating the sub information and generating a sub information code 45 from a sub information prediction signal, an abstract audition model 42 for generating the sub information prediction signal from the encoded sub information, a main information encoder 8 for encoding the frequency component 3 outputted from the band divider 2 based on the sub information 45 encoded in the adaptive sub information encoder 41 and generating a main information code 9 and a code synthesizer 10 for synthesizing the main information code 9 and the sub information code 45 and generating digital code information.