The present invention includes obtaining block type identification information on a partition of the current macroblock when the current macroblock is intra-mixed, specifying a block type of the current macroblock based on the block type identification information, obtaining an intra prediction mode of the current macroblock according to the block type of the partition of the current macroblock, and predicting the current macroblock using the intra prediction mode and a pixel value of a neighboring block.