A method of decoding an image, the method comprising: extracting information about a maximum size of a coding unit, and split information indicating whether to split a coding unit of a depth k, where k is integer, into coding units of a depth k+1, from a bitstream including encoded data of the image; determining a split structure of a square-shaped maximum coding unit, according to the split information so that the maximum coding unit is hierarchically split as a depth increases; and extracting skip information indicating whether a prediction mode of a current coding unit is a skip mode, from the bitstream, wherein the image is split into a plurality of square-shaped maximum coding units, according to the information about the maximum size of the coding unit, a maximum coding unit from the plurality of the maximum coding units is hierarchically split into one or more square-shaped coding units of depths according to the split information, a coding unit of a current depth i, where i is integer, is one of equal-sized and square-shaped data units split from a coding unit of a depth i-1, when the split information indicates a split for the coding unit of the current depth i, the coding unit of the current depth i is split into coding units of a depth i+1, independently from neighboring coding units, when the split information indicates a non-split of the coding unit of the current depth i, the coding unit of the current depth i is determined as the current coding unit which is no longer split, the skip information of the current coding unit is obtained and one or more square-shaped transformation units used to perform inverse transformation for the current coding unit are obtained from the current coding unit based on a transformation unit size information obtained from the bitstream, the one or more square-shaped transformation units being different from one or more prediction units used to perform prediction decoding for the current coding unit, when the skip information indicates that the prediction mode of the current coding unit is the skip mode, determining the current coding unit as one prediction unit of which prediction mode is the skip mode, and when the skip information indicates that the prediction mode of the current coding unit is not the skip mode, obtaining the one or more prediction units from the current coding unit by equally splitting a width or a height of the current coding unit by two, or by equally splitting both the height and the width of the current coding unit by two, or determining the current coding unit as the one prediction unit based on a partition type information of the current coding unit, the partition type information being obtained from the bitstream. extracting information about a maximum size of a coding unit, and split information indicating whether to split a coding unit of a depth k, where k is integer, into coding units of a depth k+1, from a bitstream including encoded data of the image; determining a split structure of a square-shaped maximum coding unit, according to the split information so that the maximum coding unit is hierarchically split as a depth increases; and extracting skip information indicating whether a prediction mode of a current coding unit is a skip mode, from the bitstream, wherein the image is split into a plurality of square-shaped maximum coding units, according to the information about the maximum size of the coding unit, a maximum coding unit from the plurality of the maximum coding units is hierarchically split into one or more square-shaped coding units of depths according to the split information, a coding unit of a current depth i, where i is integer, is one of equal-sized and square-shaped data units split from a coding unit of a depth i-1, when the split information indicates a split for the coding unit of the current depth i, the coding unit of the current depth i is split into coding units of a depth i+1, independently from neighboring coding units, when the split information indicates a non-split of the coding unit of the current depth i, the coding unit of the current depth i is determined as the current coding unit which is no longer split, the skip information of the current coding unit is obtained and one or more square-shaped transformation units used to perform inverse transformation for the current coding unit are obtained from the current coding unit based on a transformation unit size information obtained from the bitstream, the one or more square-shaped transformation units being different from one or more prediction units used to perform prediction decoding for the current coding unit, when the skip information indicates that the prediction mode of the current coding unit is the skip mode, determining the current coding unit as one prediction unit of which prediction mode is the skip mode, and when the skip information indicates that the prediction mode of the current coding unit is not the skip mode, obtaining the one or more prediction units from the current coding unit by equally splitting a width or a height of the current coding unit by two, or by equally splitting both the height and the width of the current coding unit by two, or determining the current coding unit as the one prediction unit based on a partition type information of the current coding unit, the partition type information being obtained from the bitstream.