A digital certificate under Public Key Infrastructure has a defect of Man-in-the-Middle Attack that performs hash collision attacks. In this paper, we propose a robust biometric-PKI authentication system against Man-in-the-Middle Attack. The biometric-PKI authentication system consists of current PKI authentication and biometric authentication, which employs biometric data and a public key from a digital certificate. In the proposed biometric-PKI authentication system, an au- thentication process performs that it extracts consistent features of fingerprint images, encrypts consistent features, and matches features with prepared templates. The simulation results of the proposed authentication system prove that our system achieves low false acceptance rate and high accuracy rate.