Provided is a method of decoding an image, the method including: determining at least one coding unit for splitting an image, based on block shape information of a current coding unit; determining at least one transformation unit, based on a shape of the current coding unit included in the at least one coding unit; and decoding the image by performing inverse transformation based on the at least one transformation unit, wherein the block shape information indicates whether the current coding unit is a square shape or a non-square shape. Also, provided is an encoding method corresponding to the decoding method. In addition, provided is an encoding apparatus or decoding apparatus capable of performing the encoding or decoding method.