Spinoza is the first and the most important political philosopher to have considered Democracy as the best government. The superiority of Democracy in Spinoza’s political philosophy is based on the metaphysical foundations of his thought. Spinoza has taken two stands regarding the human nature; on the one hand, he represents a naturalistic explanation for human-being and introduces Conatus or self-preservation as the first and the most fundamental feature of all natural beings, including human nature. On the other hand, his perfectionist metaphysical system calls for choosing a superior model for human nature by which it can be shown how to be liberated from passions of the soul and to put human beings in the limits of reason by detaching them from irrationalism of desires. Spinoza considers Democracy as superior for it is the most natural and the most rational kind of government; the most natural as it has the highest similarity with the natural state of mankind in which human is free to protect his nature and he has the right to do everything in its power; the most rational as the more the decision makers, the less the possibility of domination of ruinous and irrational passions. Our main question in this paper is how the superiority of Democracy over other governments is the outcome of metaphysical system. The central claim in this paper is that Spinoza’s assertion about superiority of Democracy is comprehensible only when we grasp his interpretation of human nature which is based on his metaphysical foundations.