Provided are a method and apparatus for encoding an image, which can variably encode a residual of a current block that is predicted with a skip mode according to prediction modes of neighboring blocks, and a method and apparatus for decoding the encoded image. When both the prediction mode of the current block and the prediction modes of the neighboring blocks are skip modes, since the method of encoding the image also encodes the residual of the current block that is predicted with the skip mode, more bits can be assigned to the current block with a high probability of acting as a reference block for other blocks.