Disclosed herein is an image decoding method. The image decoding method according to an embodiment of the present invention includes determining a prediction mode of a current block based on at least one of sizes of the current block and generating a prediction block of the current block based on the determined prediction mode. Herein, the determining of the prediction mode of the current block determines the prediction mode of the current block based on a comparison result between the size of the current block and a preset value.