The present disclosure relates to a method for processing a video signal by using a linear relationship between transform types, comprising the steps of: determining a transform group on the basis of a prediction mode of a current block; parsing a transform combination index from a video signal, wherein the transform combination index indicates anyone of a plurality of transform combinations in the transform group; deriving a transform combination corresponding to the transform combination index, wherein the transform combination consists of a horizontal transform and a vertical transform, and includes DST-7 or DCT-8; performing inverse transform on the current block on the basis of the transform combination; and restoring the video signal by using the inverse transformed current block.