According to this invention, the desired S type 2-substituted hydroxy-2-indolidinylbutyric ester compound of the formula [II]: can be prepared by reacting a 2-halo-2-indolidinylacetic ester compound of the formula [III]: wherein X is a halogen atom, R1 and R2 are a lower alkyl group, and E is an ester residue, with an R type nitrogen-containing fused heterocyclic carboxylic acid compound of the fo