An image processing apparatus includes a wavelet transform unit which applies filtering to each of one or more images having a first size into which an original image is divided, thereby producing wavelet coefficients, a quantization unit which scans and quantizes the wavelet coefficients to produce quantization coefficients, and a coding unit which scans and encodes the quantization coefficients, wherein a number of pixels in one line for the filtering and a number of pixels in one line scanned for the quantization and the encoding are selectively changed, thereby encoding an image having a second size relatively small and of frequent use without division thereof into the one or more images having the first size.