An apparatus (500, 1500) for decoding an image, the apparatus comprising: an entropy decoder (520, 1510) that performs entropy-decoding to obtain quantized transformation coefficients of at least one transformation unit in a coding unit; an inverse quantizer (530, 1520) and an inverse transformer (540, 1530) that performs inverse-quantization and inverse-transformation on the quantized transformation coefficients of the at least one transformation unit to obtain residuals, receives information about a maximum size of the coding unit, divides an image into a plurality of square maximum coding units using the information about the maximum size of the coding unit and determines the coding unit of a hierarchical structure included in a maximum coding unit, among the plurality of maximum coding units, by using information about a division shape parsed from a bitstream; and a restorer (550-580, 1540) that performs inter prediction for at least one prediction unit in the coding unit to generate a predictor and restoring the image by using the residuals and the predictor, wherein, the maximum coding unit is hierarchically split into one or more coding units of depth including at least one of a coding unit of a current depth and a coding unit of a depth greater than the current depth, according to the information about a division shape, the coding unit of the current depth is split into four equally sized 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 at least one prediction unit and is inverse-transformed using at least one transformation unit, wherein the at least one prediction unit is one among blocks including: a block equal in size to the coding unit of the depth greater than the current depth; and a block among a plurality of blocks generated by equally dividing at least one of height and width of the coding unit of the depth greater than the current depth, wherein the at least one transformation unit is one among blocks including: a block equal in size to the coding unit of the depth greater than the current depth; and a block among a plurality of blocks generated by equally dividing height and width of the coding unit of the depth greater than the current depth, and wherein, when a prediction mode is determined to be an inter prediction mode, not an intra prediction mode, the apparatus (500, 1500) for decoding the image is configured to support a transformation unit, included among the at least one transformation unit, having a size of 2N x 2N, that includes four prediction units included among the at least one prediction unit and having a size of N x N. an entropy decoder (520, 1510) that performs entropy-decoding to obtain quantized transformation coefficients of at least one transformation unit in a coding unit; an inverse quantizer (530, 1520) and an inverse transformer (540, 1530) that performs inverse-quantization and inverse-transformation on the quantized transformation coefficients of the at least one transformation unit to obtain residuals, receives information about a maximum size of the coding unit, divides an image into a plurality of square maximum coding units using the information about the maximum size of the coding unit and determines the coding unit of a hierarchical structure included in a maximum coding unit, among the plurality of maximum coding units, by using information about a division shape parsed from a bitstream; and a restorer (550-580, 1540) that performs inter prediction for at least one prediction unit in the coding unit to generate a predictor and restoring the image by using the residuals and the predictor, wherein, the maximum coding unit is hierarchically split into one or more coding units of depth including at least one of a coding unit of a current depth and a coding unit of a depth greater than the current depth, according to the information about a division shape, the coding unit of the current depth is split into four equally sized 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 at least one prediction unit and is inverse-transformed using at least one transformation unit, wherein the at least one prediction unit is one among blocks including: a block equal in size to the coding unit of the depth greater than the current depth; and a block among a plurality of blocks generated by equally dividing at least one of height and width of the coding unit of the depth greater than the current depth, wherein the at least one transformation unit is one among blocks including: a block equal in size to the coding unit of the depth greater than the current depth; and a block among a plurality of blocks generated by equally dividing height and width of the coding unit of the depth greater than the current depth, and wherein, when a prediction mode is determined to be an inter prediction mode, not an intra prediction mode, the apparatus (500, 1500) for decoding the image is configured to support a transformation unit, included among the at least one transformation unit, having a size of 2N x 2N, that includes four prediction units included among the at least one prediction unit and having a size of N x N.