PURPOSE: To recemize an optically active 2,2-dimethylcyclopropane-1-carboxylic acid alkyl ester effectively, by treating the optically active substance in the presence of an alkali metal or its hydride or its dispersion as a catalyst at a specific temperature.

CONSTITUTION: The optically active substance shown by the formula (R is alkyl) is treated in the presence of an alkali metal, its hydride, or its dispersion in a medium such as toluene, etc. at about 70W200°C, so that it is racemized effectively without causing side reactions such as acyloin condensation, etc. The compound shown by the formula is effective as an intermediate for agricultural chemicals and drugs, used as an optically active substance in many cases, however, the racemic modification is subjected to optical resolution, an effective optical active substance is separated, and the remaining antipode is racemized by the above-mentioned method, so that combination of racemization and optical resolution can convert a racemic modification into a finally effective optical active substance.