In the field of the international system, one of the important issues that arise in the proceedings is determining the validity of evidence to prove the claim. Evidence is considered as a means of proving the positions of each of the sides of the dispute in a judicial process. The most common proofs that can be presented before international institutions are written proofs and oral proofs. The purpose of the present research is to investigate the validity of the proofs of the claim in the International Court of Justice. This research is of theoretical type and the research method is descriptive-analytical and the method of data collection is library and has been done by referring to documents, books and articles. Most of the rules governing the evidence to prove the case are contained in the founding statute of the International Court of Justice; However, many evidences to prove the case are adopted from the existing procedures in the court.