In this essay, the topic which will be discussed is „St. Thomas Aquinas' Proofs of God's Existence." The first question that comes to mind when it comes to God is the question of his existence, or better said, the question is whether can we prove that God exists. St. Thomas Aquinas gave an answer to the question at the heart of every man, precisely with his proofs of God's existence. Aquinas exhibited his a posteriori evidence in five ways. Aquinas takes his first proof from experience of movement, or change, metaphysical understood as the transition of potential to the actual. Everything that moves is moved by another. This proof is considered to be the clearest and most common. The second proof concerns actual causality. It is not possible for something to be its own cause. There must be a being who is a Non-caused Cause, and this will be God alone. The third proof is about possibility and necessity. The fourth proof says that there is something that is the cause of being of all things and kindness and any other perfection and that being is who we call God. The fifth proof says that there must be an intelligent being that directs all natural things to their goal. That will be God. Also, here are presented interpretations of Thomas Aquinas proofs of God's existence, written by Croatian authors. These are Hrvoje Relja, and his Thomistic Philosophy, Ante Kusic, and his book Theodicy, Antun Bauer with his book Theodicy or the Doctrine of the Natural Knowledge of God, The Creator of the World by Franjo Sanc, and Josip Stadler with his Natural Theology. They all look back at Aquinas's proofs and interpret them.