To suppress an increase in arithmetic quantity while greatly improving encoding efficiency by a frequency analysis with high precision by a general harmonic analysis.

A high-level frequency selecting circuit 13 selects the frequency of the highest level or a plurality of frequencies of relatively high levels by processing respective frames divided by a framing circuit 11 by FFT and a high-level frequency band setting circuit 14 sets a band represented by the frequencies selected by the high-level frequency selecting circuit as a high-level frequency band extracted by a frequency component extracting circuit 12.