This paper tries to examine Heidegger's concept of ”contingency” and ”facticity” in Being and Time. The latter manifests the given situations of existence, while the former refers to the open and unknown possibilities. They signify the mode of factual existence and that of existential living of human individual respectively. Heidegger describes the ”thrownness” and ”falling” under the concept of ”facticity”, and advances the ”project” and ”resolving/resoluteness” under the concept of ”contingency/possibility”. Human life begins with the actual restricting conditions and it points toward the unknown openness. That is to say, every human activity lies between facticity and contingency. This process still involves the interaction between the ”Dasein” and the ”Other” as well as the common fate which reveals the finitude of human individual.