An image encoder/decoder by which a partial image is encoded easily with a resolution meeting the user's demand, wherein the encoded amount of data is not increased and a necessary capacity of memory can be reduced. The image encoder has a tile decomposition portion which divides image data into tiles of N pixels×M pixels, a wavelet transform coding portion which extrapolates predetermined data at the peripheries of the tiles outputted from the tile decomposition portion and performs subdivision to perform wavelet encoding. A management information generating portion generates information for managing the encoded data in order that the encoded data outputted from the wavelet transform coding portion can be decoded for each tile and for each subband of the wavelet encoding. Also, a coded data integration portion links the encoded data encoded by wavelet encoding for each tile by using the output of the management information generating portion and adds the managing information to the encoded data.