Novel bicycloester derivatives and pharmaceuticallyacceptable salts thereof have high DPP-IV inhibitory activity.SOLVING MEANSThe novel bicycloester derivatives are represented by thegeneral formula (1):(see formula 1)Pharmaceutically acceptable salts thereof are also included(Example: (2S,4S)-1-[[N-(4-ethoxycarbonylbicyclo[2.2.2]oct-1-yl)amino]acetyl]-4-fluoropyrrolidine-2-carbonitrile)).