"Political obligation" is a concept which consists of the idea of "obligation" and "political". The word "obligation" is associated with assignment, compulsion, and duty, and it has close connection with such concept like legitimacy and authority. The word "political" governs the domain of obligation or compulsion, and has close relation with such fields as ethics and religion. At first glance, the nature of such obligations seems different from social, religious, economic obligations but, the necessity to morally justify obligation in the discussion of political obligation inevitably makes it part of the ethical issues. Anyway, there have been many discussions on the concept, content, and nature of political obligation and its relationship with moral obligations and with what things are, including what voluntary actions are.Showing the conceptual difference between the synonymous words, the present paper tries to find a way to the real meaning of political obligation in order to discuss its justifying nature from the view of determinism, deontology, and finalism.