We see the universe and the objects beautiful; but some questions immediately involve our mind: »why the universe is beautiful?« and »why the human beings believe in existence of the beauty?« In this article we want to answer such questions by the descriptive - analytical method and with the emphasis on Sadraian ontology. As a result, the beauty is equivalent to existence and they are the same. Therefore, beauty as the existence is a gradation of Reality, and has various manifestations. The upmost degree of it, that is Absolute Beauty, for his perfection is essentially beautiful. Thus, universe as his effect or manifestation is beautiful too. By awareness of Absolute Beauty as the cause or the Lightening and by seeing ourselves and other beautiful things as its effect or manifestation, we believe in existence of beauty.