An apparatus for decoding a video, the apparatus comprising: a receiver configured to receive a bitstream of an encoded video; an extractor configured to extract, from the bitstream, information about a maximum size of a coding unit which is a data unit in which a picture is decoded, and information about a coded depth and an encoding mode for coding units of the picture; a decoder configured to split the picture into a plurality of maximum coding units using the information about the maximum size of the coding unit; and decode the picture based on coding units of a hierarchical structure split from each maximum coding unit among the plurality of maximum coding units, using the information about a coded depth and an encoding mode, wherein: the information about a coded depth comprises split information indicating whether a coding unit of a current depth, among the coding units, is split into coding units of a lower depth, the encoding mode comprises information about a partition type of a coding unit of the coded depth among the coding units, information about a prediction mode of the coding unit of the coded depth and information about a size of a transformation unit of the coding unit of the coded depth, the each maximum coding unit is hierarchically split into coding units of at least one depth according to the split information, and when the split information indicates a split for the coding unit of a current depth, among the coding units of at least one depth, the decoder determines the coding units of a lower depth by dividing a height and width of the coding unit of a current depth by two, and when the split information indicates that the coding unit of a current depth is no longer split as the coding unit of the coded depth, the decoder determines at least one prediction unit obtained from the coding unit of the current depth by using the information about a partition type, performs prediction on the coding unit of the current depth based on the at least one prediction unit by using the information about a prediction mode, determines at least one transformation unit obtained from the coding unit of the current depth by using the information about a size of a transformation unit and performs inverse transformation on the coding unit of the current depth based on the at least one transformation unit. a receiver configured to receive a bitstream of an encoded video; an extractor configured to extract, from the bitstream, information about a maximum size of a coding unit which is a data unit in which a picture is decoded, and information about a coded depth and an encoding mode for coding units of the picture; a decoder configured to split the picture into a plurality of maximum coding units using the information about the maximum size of the coding unit; and decode the picture based on coding units of a hierarchical structure split from each maximum coding unit among the plurality of maximum coding units, using the information about a coded depth and an encoding mode, the information about a coded depth comprises split information indicating whether a coding unit of a current depth, among the coding units, is split into coding units of a lower depth, the encoding mode comprises information about a partition type of a coding unit of the coded depth among the coding units, information about a prediction mode of the coding unit of the coded depth and information about a size of a transformation unit of the coding unit of the coded depth, the each maximum coding unit is hierarchically split into coding units of at least one depth according to the split information, and when the split information indicates a split for the coding unit of a current depth, among the coding units of at least one depth, the decoder determines the coding units of a lower depth by dividing a height and width of the coding unit of a current depth by two, and when the split information indicates that the coding unit of a current depth is no longer split as the coding unit of the coded depth, the decoder determines at least one prediction unit obtained from the coding unit of the current depth by using the information about a partition type, performs prediction on the coding unit of the current depth based on the at least one prediction unit by using the information about a prediction mode, determines at least one transformation unit obtained from the coding unit of the current depth by using the information about a size of a transformation unit and performs inverse transformation on the coding unit of the current depth based on the at least one transformation unit.