An image processing apparatus and an image processing method are disclosed for generating coded data having a desired data size at a high speed. The image processing apparatus includes a coding part, two memories, a setting part and a data size adjustment part. The coding part partitions a wavelet coefficient of image data into bit-planes and generates coded data of the image data through entropy coding on the wavelet coefficient for each of the bit-planes. The data size adjustment part adjusts a size of the coded data such that the size falls within an acceptable range including the target size set by the setting part by sequentially discarding a portion of the coded data in a least significant order based on the size of the coded data portion corresponding to each of the bit-planes.