The present invention relates to a method for decoding a video signal, comprising: obtaining adaptive transform size flag information for a 1st coding unit, the adaptive transform size flag information indicating whether a coding unit is partitioned in to coding units each of which has a half size in horizontal and vertical directions; obtaining adaptive transform size flag information for each 2nd coding unit, if the adaptive transform size flag information of a 1st coding unit is true, the 2nd coding unit indicating a sub-block included in the 1st coding unit; determining a size of a transform unit based on the adaptive transform size flag information; wherein the adaptive transform size flag information is obtained based on a size of a current transform unit, a minimum transform size, and a maximum transform size.