A compound represented by formula (I); 1 wherein ring A represents a nitrogen containing heterocyclic ring, ring B represents 5-membered heterocyclic ring which may have substituents, R represents a hydrogen atom or cyano and the other symbols represent as described in the specification; or a salt thereof. The compound represented by formula (I) has an inhibitory activity of DPP-IV, and therefore is useful as a preventive and/or treatment agent for type 2 diabetes mellitus, obesity, autoimmune disease, cancer metastasis, AIDS virus infection, dermatosis, prostatic hypertrophy and the like