A method of decoding 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, determining that 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 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, wherein, when the split transformation flag indicates a split for the current depth, a transformation unit of the current depth is split into one or more transformation units of a next depth, and a split transformation flag for the next depth is obtained from the bitstream. 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, determining that 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 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, wherein, when the split transformation flag indicates a split for the current depth, a transformation unit of the current depth is split into one or more transformation units of a next depth, and a split transformation flag for the next depth is obtained from the bitstream. 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, wherein, when the split transformation flag indicates a split for the current depth, a transformation unit of the current depth is split into one or more transformation units of a next depth, and a split transformation flag for the next depth is obtained from the bitstream.