As is known by all, the main body of International Law is the state, in its widest definition it includes international organizations and individuals which are a limited body. So how do we define 'private' terrorist organizations in International Law? Traditional Law of War only regarded the violence organized by national regular armies as a legal act; the violence organized by personal organizations was only a general crime. Originally the Law of War was only applicable to military force disputes between sovereign states, but nowadays, it is expanding its application to military disputes between states and traitors which are not part of the main body of state, or military conflicts between forces which are both 'non main body of state'. The Law of War is applicable to military conflicts between military organizations of non state agency. And there are acts of non regular armies in military disputes between states. Nowadays some terrorist organizations even possess destructive capabilities not less strong than small sovereign states. So terrorist acts no longer can be simply dealt with under 'crime of private organizations'. Under these circumstances, can 'terrorist organizations' be considered under the main-body-to-be of International Law and under application of the Law of War? Should the Law of War cover 'terrorist acts held by private organizations' apart from 'war held by state'? These are the subjects we'll discuss in this essay.