To enhance the usable life of existing building, a strengthening method with bonding CFRP plates has been
developed by authors. The CFRP plates is high-strength(2100MPa) in longitudinal normal stress. The composite of steel bonding CFRP may easily peel out under tensile loading because shear bonding stress is concentrated at the edge of CFRP Plates. In this paper, F.E.M. was performed to investigate the nature of the case of the non-adhesive edge of the CFRP Plates. Also, tensile loading tests of composite of steel bonding CFRP plates were performed to clarify failure condition of adhesive. Failure condition of adhesive was investigated by comparing with the theoretical solution.