This paper intends to provide an analysis of Whitehead's view of Substance in its traditional or Aristotelian sense based on his process cosmological principles. According to this analysis, he sees the roots of modern scientific materialism in Aristotelian Substance and, following this, replaces the concept of Substance with the concept of actual being within the framework of his own philosophy. The important point is that this does not mean his total rejection of Substance. In fact, we can say that, on the one hand, Whitehead has a negative view of Substance in the sense that he sees it inconsistent with his own cosmological principles from an ontological point of view and rejects it. On the other hand, he has a positive view of Substance and considers it useful for common purposes of life in linguistic and practical respects. Therefore, it is concluded that, although Whitehead has seriously criticized Aristotelian Substance and even substituted it with another concept, he has not totally rejected it.