Provided is an image encoding apparatus that generates a prediction block according to an intra prediction mode, generates a residual block, transforms the residual block to generate a transform block, quantizes the transform block to generate a quantized transform block, scans the quantized transform block to generate one-dimensional (1D) quantized coefficients, and entropy-codes the 1D quantized coefficients. When a size of the transform block is 8×8, the quantized transform block is divided into a plurality of sub-blocks after quantization of the transform block, the plurality of sub-blocks are scanned using a first scan pattern determined according to the intra prediction mode, and coefficients of each sub-block are scanned using a second scan pattern determined according to the intra prediction mode. The first scan pattern is a scan order applied to the plurality of sub-blocks. The second scan pattern is a scan order applied to the coefficients of each sub-block.