Analysis filter processing is recursively repeated on horizontal and vertical low frequency component coefficients obtained as a result of the analysis filter processing, until a predetermined decomposition level is reached. Coefficients obtained during a process of computation in the analysis filter processing and, except for a preset decomposition level, horizontal and vertical low frequency component coefficients obtained as a result of the computation in the analysis filter processing are stored in a first storage section independently for each decomposition level. The coefficients stored in the first storage section are read as appropriate and the read coefficients are supplied for the analysis filter processing. The horizontal and vertical low frequency component coefficients of the preset decomposition level are stored in a second storage section. The coefficients stored in the second storage section are read as appropriate. The read coefficients are supplied for the analysis filter processing.