This research comprises of two parts. The first part analyses the most important issues of the principle of Member State’s liability in damages for the breach of European Union law: legal basis of the principle, requirements for liability and, lastly, recent developments in the case law of the Court of Justice of the European Union. The principle of Member State’s liability in damages and the requirements of liability are being further developed by the Court in its modern jurisprudence. These cases show that the requirements of liability were clarified and the scope of application of the principle of Member State’s liability broadened. The author also examines that the state liability is being recognised both in EU and international law. State responsibility in international law can be understood in a broad sense and a narrow sense. It is emphasized that in a broad sense, state responsibility in international law comprises three institutes: firstly, state responsibility for internationally wrongful acts; secondly, state responsibility for the damage caused by lawful acts.