PURPOSE: To provide a smooth synthesis waveform with the number of less bits and to provide a reproducing voice of high quality with less operation amounts by coding respective frequency spectrum information of a sine synthesis wave and a noise.

CONSTITUTION: An inverse filter circuit 21 performs inverse filter processing by an updated a parameter to obtain a smooth output. The output of the inverse filter circuit 21 is sent to a harmonics/noise coding circuit 22, to put it concretely, e.g. a multi-band excitation (MBE) analysis circuit. The harmonics/noise coding circuit or the MBE analysis circuit 22 analyzes the output from the inverse filter circuit 21 by a method equal to e.g. MBE analysis. In such a case, a short term predictive remainder such as an LPC (linear predictive coding) remainder, etc., of an input voice signal is expressed with the sine synthesis wave and the noise by the MBE analysis, etc., and respective frequency spectrum information of respective sine synthesis wave and noise are coded.