To obtain the subject optically high-purity compound by a simple operation by treating a raw material compound of racemic modification with an optically active amine, subjecting formed diastereomer salts to optical resolution by using difference in solubility and decomposing an obtained slightly soluble optically active diastereomer salt.

A (±)-4-carbamoyl-3-(dihalogeno-substituted phenyl)lactic acid [e.g. (t)-4-carbamoyl-3-(3,4-dichlorophenyl)lactic acid or the like] is treated with an optically active amine (e.g. α-methylbenzylamine or the like). Formed diastereomer salts are subjected to optical resolution by crystallization using difference in solubility. An obtained slightly soluble optically active diastereomer salt is decomposed by a neutral reaction to give an optically active 4- carbamoyl-3-(dihalogeno-substituted phenyl)lactic acid of the formula (X is a halogen).