Provided are an image encoding/decoding method and device. The image decoding method performed by the image decoding device, according to the present disclosure, may comprise the steps of: determining a residual sample of a current block; and resetting the value of the residual sample on the basis of whether a color space transform is applied. The step for resetting the value of the residual block may be performed on the basis of a half value of a chroma residual sample value.