Field and Aims: The right to freedom of religious belief is one of the recognized human rights endorsed by Islamic jurisprudence, the Iranian constitution and international documents. However, the departure of a Muslim from Islam and his entry into infidelity has been identified in the form of apostasy, and punishment has been prescribed for it in the Shari'a. Accordingly, we seek to answer the questions that, first of all, the existence of punishment for apostasy is not in conflict with the right to freedom of religious belief? Also, what is the approach of the Iranian penal system and international documents to this issue of apostasy? Methodology: This article is written in an analytical-descriptive manner. Findings and Conclusion: In reading Islamic texts, restrict verses, narrations, and verses, and dispel doubts and arguments. Also, verses that specify the principle of freedom of belief, all of them in a position to accept the principle of religion But after accepting Islam, he is deprived of the right to return along with promotion, propaganda and conspiracy. Considering that apostasy is defined in international documents, especially the 1951 Refugee Convention and the European Convention on Human Rights, in the category of political crimes, which is an exception to the extradition of criminals, so it is not possible to extradite convicts to apostasy. In Iran's criminal policy, there is a possibility of being sentenced to the most severe punishment for apostasy. Also, Iran's political crime law confirms the non-extradition of a political offender, but is silent about apostasy and does not say how it is carried out.