A method of decoding an image, the method comprising: obtaining quantized transformation coefficients of a transformation unit in a coding unit by performing entropy decoding on a bitstream encoded based on the coding unit; obtaining residuals of the transformation unit by performing inverse quantization and inverse transformation on the quantized transformation coefficients; and performing prediction using at least one prediction unit included in the coding unit to generate a predictor, and reconstructing the coding unit using the residuals and the predictor, determining a plurality of square maximum coding units in an image based on information about a maximum coding unit extracted from the bitstream, determining one or more square coding units of depth including at least one of a current depth and a depth greater than the current depth that are hierarchically split from the maximum coding unit based on information about coding units extracted from the bitstream, wherein the coding unit of the current depth is split into four square coding units of a depth greater than the current depth, independently from neighboring coding units of the current depth, and the coding unit of the depth greater than the current depth is predicted using the at least one prediction unit, wherein the at least one prediction unit is one of a block equal in size to the coding unit of the depth greater than the current depth, and a block from among a plurality of blocks generated by equally dividing at least one of a height and a width of the coding unit of the depth greater than the current depth, wherein the transformation unit is one of a block equal in size to the coding unit of the depth greater than the current depth, and a block from among a plurality of blocks generated by equally dividing the height and width of the coding unit of the depth greater than the current depth, and characterised in that the method of decoding supports the transformation unit having a size of 2Nx2N that includes four prediction units having a size of NXN. obtaining quantized transformation coefficients of a transformation unit in a coding unit by performing entropy decoding on a bitstream encoded based on the coding unit; obtaining residuals of the transformation unit by performing inverse quantization and inverse transformation on the quantized transformation coefficients; and performing prediction using at least one prediction unit included in the coding unit to generate a predictor, and reconstructing the coding unit using the residuals and the predictor, determining a plurality of square maximum coding units in an image based on information about a maximum coding unit extracted from the bitstream, determining one or more square coding units of depth including at least one of a current depth and a depth greater than the current depth that are hierarchically split from the maximum coding unit based on information about coding units extracted from the bitstream, wherein the coding unit of the current depth is split into four square coding units of a depth greater than the current depth, independently from neighboring coding units of the current depth, and the coding unit of the depth greater than the current depth is predicted using the at least one prediction unit, wherein the at least one prediction unit is one of a block equal in size to the coding unit of the depth greater than the current depth, and a block from among a plurality of blocks generated by equally dividing at least one of a height and a width of the coding unit of the depth greater than the current depth, wherein the transformation unit is one of a block equal in size to the coding unit of the depth greater than the current depth, and a block from among a plurality of blocks generated by equally dividing the height and width of the coding unit of the depth greater than the current depth, and characterised in that the method of decoding supports the transformation unit having a size of 2Nx2N that includes four prediction units having a size of NXN.