This article is on Jean-Paul Sartre’s existentialist philosophy and his theory of art. Sartre, first of all, sets up phenomenological ontology, then founds humanist atheist existentialism. Sartre projects his theory of committed literature as his contribution to the field of philosophy of art on phenomenological ontology and humanist atheist existentialism. In the first part of this article, a brief description of the sources and grounds of Sartre’s ideas are given. In the second part, the theory of committed literature is explained. (...) Here, the most important property of Sartre’s art theory, namely Sartre’s separation of literature from plastic arts is clarified. The second part of the article is composed of four sections. In the first section of the second part, Sartre’s critique against the theory of aesthetic purity is investigated. In the second section, a relation between development of art and human freedom is set up. In the third section the difference between art of literature and plastic arts is determined. In the fourth and the last section the meaning of committed literature is defined. (shrink)