A fixed code book (FCB) search device simplifies an error minimizing process and reduces a calculation amount so as to prevent deterioration of a coding performance. The FCB search device includes a pulse shape convolution inverse filter having an inverse feature of a pulse diffusion filter and supplied with an ideal residual signal; a pulse candidate preparatory selector that pre-selects a plurality of pulse candidates from the ideal residual signal to which the inverse filter is applied; and a pulse candidate final selector that finally selects one pulse from the selected candidates. Using this configuration, a search is made for an algebra code book to which the pulse diffusion is applied.