It is well known that Deleuze began his philosophical work from researching the biographies of many predecessors' such as D. Hume, Lucretius, I. Kant, B. Spinoza, F. W. Nietzsche, H. Bergson, and etc. Among them, especially Spinoza, Nietzsche, and Bergson constitute a foundation supporting the whole idea of Deleuze. He declared that the goal of his early biographical work is a theme converging the identity of two philosophers, Spinoza and Nietzsche, and it shows that these two philosophers had such a huge significance to Deleuze, at least by then. However, we may point out two issues here. The first is why Deleuze, who is recognized as a philosopher of 'difference', deals the identity. The other issue is, what kind of identity exists between the two philosophers, Spinoza and Nietzche. In a common sense, their ideas contradict to each other. Spinoza puts God at the center of his philosophical system, whereas Nietzsche declared 'God is dead'. Though Nietzsche expressed a concurrent opinion with Spinoza at first, it is well known that he turned his side against him soon after and criticized him sharply. There is a conflict at the core of this criticism concerning the existence or non-existence of God. Many think that Spinoza, however, cannot be free from the argument that his philosophy allows a possibility of atheism. Deleuze, who also called Spinoza an atheist, suggested a new viewpoint of the philosophy of Spinoza based on his attribution to the concept of 'power'. On the other hand, Deleuze reinterpreted Nietzsche, where he analyzed 'the will to power' in a totally inventive way. Likewise, the reciprocal communication of ideas connected by the concept of 'power' gives a foundation of identifying the two philosophers to Deleuze. In this paper, considering this reciprocal communication, I intent to reveal the foundation of identity of the two philosophers, Spinoza and Nietzsche, and as a result, investigate what the concept of identity means to Deleuze, the philosopher of difference. Furthermore, we will also take a look at how Deleuze presents a new perspective on the conflict on the existence of God of the two philosophers in the process of validating the identity.