1. A wavelet processing apparatus comprising: a readout block for reading out data in unit of a region obtained by decomposing an image into a plurality of regions while adding to the data within the region excess data of a predetermined data number outside the region; a line-based wavelet transform block for performing a line-based wavelet transform on the data read out at the readout block while decomposing the band of the data in a plurality of decomposition levels; and a data extraction block for extracting the data that has been subjected to the line-based wavelet transform at said line-based wavelet transform block in a predetermined format.