Disclosed are a method for decoding a video signal and an apparatus therefor. Specifically, a method for decoding an image may include: partitioning a current coding tree block into a plurality of coding blocks so that coding blocks partitioned from the current coding tree block are included in a current picture when the current coding tree block is out of a boundary of the current picture; parsing a first syntax element indicating whether a current coding block is partitioned into a plurality of subblocks when the current coding block satisfies a predetermined condition; and determining a split mode of the current coding block based on the syntax element.