A video decoding apparatus comprising: an extracting unit which obtains, from a bitstream, transformation-unit hierarchical-structure information comprising maximum split information for a transformation unit with an intra mode, maximum split information for a transformation unit with an inter mode and information about a prediction mode for a coding unit, wherein the maximum split information for the transformation unit with the intra mode is a total number of allowable levels of transformation units with respect to a coding unit predicted according to the intra mode, wherein the maximum split information for the transformation unit with the inter mode is a total number of allowable levels of transformation units with respect to a coding unit predicted according to the inter mode, and wherein the maximum split information for the transformation unit with the intra mode and the maximum split information for the transformation unit with the inter mode are separately determined; and a decoding unit which determines a maximum split level of a transformation unit based on the maximum split information for the transformation unit with the intra mode when the information about the prediction mode indicates that the coding unit is predicted according to the intra mode, and determines a maximum split level of a transformation unit based on the maximum split information for the transformation unit with the inter mode when the information about the prediction mode indicates that the coding unit is predicted according to the inter mode, wherein the decoding unit performs inverse-transformation on the coding unit predicted according to the intra mode or the inter mode by using transformation units in a variable tree-structure which are determined from a base transformation unit with respect to the coding unit, and which are generated based on the determined maximum split level of the transformation unit, wherein a size of the base transformation unit corresponds to a size of the coding unit. an extracting unit which obtains, from a bitstream, transformation-unit hierarchical-structure information comprising maximum split information for a transformation unit with an intra mode, maximum split information for a transformation unit with an inter mode and information about a prediction mode for a coding unit, wherein the maximum split information for the transformation unit with the intra mode is a total number of allowable levels of transformation units with respect to a coding unit predicted according to the intra mode, wherein the maximum split information for the transformation unit with the inter mode is a total number of allowable levels of transformation units with respect to a coding unit predicted according to the inter mode, and wherein the maximum split information for the transformation unit with the intra mode and the maximum split information for the transformation unit with the inter mode are separately determined; and a decoding unit which determines a maximum split level of a transformation unit based on the maximum split information for the transformation unit with the intra mode when the information about the prediction mode indicates that the coding unit is predicted according to the intra mode, and determines a maximum split level of a transformation unit based on the maximum split information for the transformation unit with the inter mode when the information about the prediction mode indicates that the coding unit is predicted according to the inter mode, wherein the decoding unit performs inverse-transformation on the coding unit predicted according to the intra mode or the inter mode by using transformation units in a variable tree-structure which are determined from a base transformation unit with respect to the coding unit, and which are generated based on the determined maximum split level of the transformation unit, wherein a size of the base transformation unit corresponds to a size of the coding unit.