This article is an attempt to inquire into the doctrine of papal primacy in Gregorius VII and Martin Luther, focusing on their biblical interpretations of Matthew 16:18-19 and John 21:15-17. Gregorius VII refers to these passages as the scriptural evidence for Petrine primacy and monopolistic privileges. Furthermore, unambiguously revealing an invincible conviction of himself as the vicar of Christ and Peter's successor, Gregorius VII materializes an unprecedented form of papal primacy, not only in theory but also in practice. He plays his role as the head in the secular realm as well as in the spiritual one. He demands the kind of obedience that should be shown to Christ or St. Peter, the Prince of the Apostles, from both religious and secular leaders. Luther advances divergent interpretation of these passages. The significant characteristic of his interpretations is that they are Christological, or more precisely, Christocentric. This reveals that the essence of Luther's Reformation thought, that is, his theological stance on Jesus Christ and faith in him, is functioning as the interpretive key to these passages. The “rock” is defined as Jesus Christ or faith in him. He builds a Christian community comprised of those who believe in him. So Christ is the sole head of this spiritual community of believers, who properly wield the power of the two keys to bind and loose sins. Luther argues that, when Jesus asked Peter to tend his sheep, his command is irrelevant to papal primacy in both spiritual and secular realm. Luther pays heed to the question “Do you love me?,” which Jesus Christ asked Peter three times. Based on this question, Luther contends that no one can tend Christ’s sheep without loving him genuinely in the first place. Tending Christ’s sheep means following his steps and offering voluntary service to others.