Finite biprefix codes whose syntactic monoids are groups were studied by M.P. Schutzenberger. P. Udomkavanich gave a characterization of finite inverse biprefix codes (codes admitting finite inverse semigroups as their syntactic monoids). An example of finite inverse biprefix code whose syntactic monoid contains a nonabelian group, S3, was given. In this research, we will investigate subgroups of syntactic monoids of finite inverse biprefix codes.