1. A video decoding method comprising: obtaining, from a bitstream, a split transformation flag indicating whether a transformation unit included in a coding unit is split; obtaining a current transformation unit from the coding unit based on the split transformation flag; determining a context model using a context model index determined based on a size of the current transformation unit and a value of a color component index of a picture to which the current transformation unit belongs, without using any syntax elements from blocks neighboring the coding unit, wherein the color component index is set with respect to a luminance color component, a first chrominance color component, and a second chrominance color component, and the color component index for the luminance color component has a value of zero, the color component index for the first chrominance color component has a value of one, and the color component index for the second chrominance color component has a value of two; obtaining a transformation coefficient flag indicating whether there exists a non-zero coefficient in a block of the current transformation unit by decoding the bitstream using Context Adaptive Binary Arithmetic Coding (CABAC) based on the context model; and obtaining a transformation coefficient included in the current transformation unit based on the transformation coefficient flag, wherein the decoding the bitstream using Context Adaptive Binary Arithmetic Coding (CABAC) further comprises: determining a Most Probable Symbol (MPS) between 0 and 1 based on the context model; determining a probability state index based on the context model; and decoding the bitstream based on the determined MPS and the probability state index.