A process for synthesizing adipic acid comprising the steps of using glucaric acid or galactaric acid as a starting material, using rhenium catalyst and acid catalyst, using one or more reaction solvents selected from a group consisting of heptanol and butanol; and b) subjecting glucaric acid ester or galactaric acid ester obtained from the step a) to hydrogenation reaction with precious metal catalyst, and then hydrolyzing the ester obtained from this reaction to obtain adipic acid.