Disclosed herein is a video decoding method including: obtaining a transform skip mode flag indicating whether transform/inverse transform is skipped in a current block; when transform/inverse transform is skipped in the current block according to the transform skip mode flag, determining that secondary transform/inverse transform is skipped in the current block; and when transform/inverse transform is not skipped in the current block according to the transform skip mode flag, obtaining a transform matrix index for secondary transform/inverse transform of the current block and, determining whether secondary transform/inverse transform is skipped in the current block based on the transform matrix index.