1. A method of decoding video, the method comprising: obtaining a bin string corresponding to current transformation coefficient level information by arithmetic decoding a bitstream; determining a current binarization parameter, for determining a prefix bin string from the bin string, to be one of (i) a previous binarization parameter and (ii) an updated value of the previous binarization parameter obtained by adding n to the previous binarization parameter, where n is an integer, and n is equal to or greater than 1, based on a comparison between a predetermined value that is proportional to the previous binarization parameter and a value of a previous transformation coefficient; obtaining the current transformation coefficient level information by de-binarizing a binary value of the prefix bin string using the determined current binarization parameter; determining a value of the current transformation coefficient using the current transformation coefficient level information; and decoding data included in a transformation unit using reverse transformation based on the value of the current transformation coefficient in the transformation unit, wherein, when the value of the previous transformation coefficient is equal to or smaller than the predetermined value, the current binarization parameter is determined to be the previous binarization parameter, and when the value of the previous transformation coefficient is larger than the predetermined value, the current binarization parameter is determined to be the updated value.