A video signal processing method and device for encoding or decoding a video signal are disclosed. The video signal processing method comprises the steps of: identifying a tree type of a current chroma block; deriving a chroma intra prediction mode of the current chroma block on the basis of a luma intra prediction mode at a preset position if the tree type of the current chroma block is a dual tree; generating a prediction block of the current chroma block on the basis of the chroma intra prediction mode; and restoring the current chroma block by adding a residual block of the current chroma block to a prediction block, wherein the luma intra prediction mode can be set to a preset mode if the luma prediction mode at the preset position is an intra block copy mode.