The present invention aims at providing an optically active difluoromethanesulfonanilide derivative exhibiting an excellent herbicidal activity at a low dose.An optically active (R)-2′-(4,6-dimethoxy-pyrimidin-2-yl)hydroxymethyl-1,1-difluoromethanesulfonanilide derivative is represented by the formula (I) (in the formula, R1 is a hydrogen atom, a C1-C4 alkyl group or a C1-C4 alkoxy C1-C4 alkyl group). and this difluoromethanesulfonanilide derivative is produced by subjecting to optical resolution a racemate of 2′-(4,6-dimethoxypyrimidin-2-yl)hydroxymethyl-1,1-difluoromethanesul-fonanilide derivative.