A process for producing a high purity 3,5-dihydroxy6-heptenoic acid derivative by controlling the content of impurities such as denatured substances, is provided. When a 3,5-dihydroxy-6-heptenoic acid derivative is produced by a process which comprises a step of contacting the 3,5-dihydroxy-6-heptenoic acid derivative of the formula (1) wherein R is a C.sub.1-4 alkyl group, with a C.sub.1-4 lower alcohol-containing solvent, an alcohol containing solvent having its content of an oxidizing substance lowered, is used to at most 0.05 molar equivalent to a 3,5-dihydroxy-6-heptenoic acid derivative, to suppress impurities contained in the 3,5-dihydroxy-6heptenoic acid derivative. ##STR00001##