To provide a sub-band coding and decoding method for a digital audio signal that reduces a delay amount while maintaining its compression rate and to enhance decoding reproduction quality.

A sub-band division processing section 101 applies band split filtering to a received PCM audio signal to decimate the signal. A table value introduction section 106 introduces a table value from a scale factor obtained by a scale factor extract section 104 and a sub-band combining and processing section 107 calculates a combined waveform based on the table value of a preceding scale factor. An energy or maximum value calculation section 108 calculates a maximum value or energy of the combined waveform. A bit assignment processing section 110 calculates a sample assignment bit quantity based on a masking level calculated by an psychroacoustic model 109 and a quantization processing section 111 quantizes a sub-band signal. A frame forming section 112 forms a sign bit, a Huffman code and a sample into a bit stream and outputs the result. Since the processing is conducted with a very short frame, the delay quantity is small.