"Philosophy" is "to do philosophy." The first and fundamental problem of philosophy is philosophy in itself; and it is a constant relation in which it relates to itself, as G. Simmel said. And in this point consists the "Wesenseigentumlichkeit" which distinguishes itself fundamentally from other sciences. It is too famous that Kant has said about the essence of "Philosophy" like this; Man can not study "Philosophy", except "to do philosophy". According to the above-mentioned view-point, only those who carried on their shoulders all their lives the task of studying real philosophy, in other words only those who continued ernestly "to do philosophy" throughout lives, are the true Philosophers. And I saw such a philosophical existence in Soren Kierkegaard, first of all. Of course, I can recognize F. Nietzsche as a representative philosopher of such kind, as Jaspers indicated. But it is S. Kierkegaard who makes me (my existence) selfconscious of its own theme, and also presented me the way of looking into its problem; namely it is S. Kierkegaard who teaches me the true philosophy. In this reason I selected S. Kierkegaar rather than Nietzsche as a theme of my study. What is the characteristic of S. Kierkegaard's philosophy? It is that he took out "thought" from the deepest bottom of human existence, made it the object of doubt, asked for its possibility fundamentally, and by having spiritual attitude of continuing "to do Philosophy" all his life, he presented a new attitude, namely "eine neue denkende Gesamthaltung des Menschen (Jaspers)", mediating infinite reflexion, being self-conscious of the fact that he can not obtain any ground for his reflextion, witout bringing any theory, fundamental stand-point or one world-image. In case of Kierkegaard, "to do philosophy" was presentation of "die denkende Gesamthaltung des Menschen". What this essay is seeking for, is Kierkegaard's thought-attitude, which was presented in the precedent paragraphy. More concretely speaking, object of this research is to clarify not only outer form, but also inner structure of his thought-method.