A process for producing an optically active olefin represented by a formula ##STR1## wherein R.sup.1 represents an organic group and X represents a polycyclic carbon ring group, by reacting a corresponding optically active ester derivative represented by a formula ##STR2## wherein R.sup.1 and X are as defined above and R represents a hydrogen atom, an alkoxy group, an alkenyloxy group or a substituted or unsubstituted aralkyloxy group, with formic acid or a salt thereof in the presence of a catalyst comprising a palladium salt and a tertiary phosphine.Said process makes it possible to produce, at a high yield at a high selectivity, an optically active olefin which has a physiological activity and is useful as a medicine or is useful as an intermediate for the synthesis of physiologically active steroids. Further, said process uses no harmful reagent such as mercury or the like. Thus, it is advantageous as an industrial process.