Öz The main aim of this presentation is to explain and analyse the primordial thinking structure of Heraclitus’ philosophy according with the basis of German philosopher Martin Heidegger’ philosophy, especially in the ontology of his interpretation of pre-Socratic philosophy. Heidegger holds that Anaximander, Parmenides, and Heraclitus were the only primordial thinkers because they thought the beginning, Being. These Pre-Socratics represent the most significant historical philosophical period because they asked the most primordial philosophical question, the question of Being, Seinsfrage. Rainer Martin calls Heidegger's understanding of the primordial thinking as beginning and non-primordial thinking as inception. At the Beginning of philosophy, there were many philosophers, but only a few of them thought "Beginn". Heidegger distinguishes these from the rest of the Greek philosophers. Heraclitus' thinking is presented in contrast to Parmenides' thought of Being. For Heraclitus, everything is in flux; so everything is becoming. For Heidegger, this distinction runs through the whole history of philosophy. However, Heidegger points out that the doctrine of becoming must not be interpreted at the same level with Darwinism because the contrast of becoming and Being is represented in Greek thought uniquely and self-sufficiently and not as in later thoughts.Heidegger maintains that although the distinction between Being and appearance is equally primordial with the distinction between Being and becoming, the connection has been inaccessible to us. Heidegger explains the distinction between Being and appearance in the following quotation: "At first sight the distinction seems clear. Being and appearance means: The real in contradistinction to the unreal, the authentic over against the inauthentic."