The article is a research of international criminal law as a legal basis of international criminal justice and their interaction. The author examined theoretical grounds of the concept of international criminal justice. Fundamental ideas taken as a basis for a concept of international criminal justice and which have an impact on its development were analized. Doctrine of international legitimacy was investigated in terms of the rule of law aimed at protection of universal values of today’s globalized world and which acts as theoretical justification of international criminal justice. The author considered stages of formation and development of international criminal law. It is stated that a final establishment of international criminal law as a legal basis of international criminal justice has taken place since the Rome Statute of the International Criminal Court came into effect and the Court started its work. Particular emphasis was given to issues of jurisdiction of the International Criminal Court as one of the key elements of the system of international criminal justice. Analysis of academic views as regards a role and place of international criminal law in the system of international law was provided. On the grounds of analysis of subject and method of legal regulation it is proved that modern international criminal law serves as an independent branch of international law. The author gives its own definition of international criminal law generally and properly. He also stressed the effect of international criminal law on the domestic criminal law including criminal law of Ukraine.