A decoding method of a video, the method comprising: obtaining, from a bitstream, a split transformation flag for a current depth, and when the split transformation flag indicates non-split for the current depth, determines a transformation depth is equal to the current depth; obtaining at least one transformation unit from a coding unit based on the split transformation flag; determining a context increasement parameter for determining a context index based on only whether the transformation depth is equal to zero or not, and obtaining a context model for arithmetically decoding a transformation unit significant coefficient flag of a luma component indicating whether a non-zero transformation coefficient exists in the transformation unit of the luma component, using the context index obtained by adding the context increasement parameter and a context offset; arithmetically decoding the transformation unit significant coefficient flag based on the determined context model; and determining whether at least one non-zero transformation coefficient exists in the transformation unit of the transformation depth, based on the transformation unit significant coefficient flag, wherein the transformation depth indicates number of times the coding unit is split to determine the transformation unit included in the coding unit, wherein the determining the context increasement parameter further comprising: when the transformation depth is equal to zero, determining the context increasement parameter as one; and when the transformation depth is not equal to zero, determining the context increasement parameter as zero, when the split transformation flag for a current transformation unit of a current transformation depth k indicates a split, the current transformation unit of the current transformation depth k is split into four transformation units of a lower transformation depth (k+1). obtaining, from a bitstream, a split transformation flag for a current depth, and when the split transformation flag indicates non-split for the current depth, determines a transformation depth is equal to the current depth; obtaining at least one transformation unit from a coding unit based on the split transformation flag; determining a context increasement parameter for determining a context index based on only whether the transformation depth is equal to zero or not, and obtaining a context model for arithmetically decoding a transformation unit significant coefficient flag of a luma component indicating whether a non-zero transformation coefficient exists in the transformation unit of the luma component, using the context index obtained by adding the context increasement parameter and a context offset; arithmetically decoding the transformation unit significant coefficient flag based on the determined context model; and determining whether at least one non-zero transformation coefficient exists in the transformation unit of the transformation depth, based on the transformation unit significant coefficient flag, wherein the transformation depth indicates number of times the coding unit is split to determine the transformation unit included in the coding unit, wherein the determining the context increasement parameter further comprising: when the transformation depth is equal to zero, determining the context increasement parameter as one; and when the transformation depth is not equal to zero, determining the context increasement parameter as zero, when the transformation depth is equal to zero, determining the context increasement parameter as one; and when the transformation depth is not equal to zero, determining the context increasement parameter as zero, when the split transformation flag for a current transformation unit of a current transformation depth k indicates a split, the current transformation unit of the current transformation depth k is split into four transformation units of a lower transformation depth (k+1).