Basically, gender does not result in differences of punishment, but in Islamic legal system, and as a result in the current regulations in the Islamic republic of Iran, one can see such differences. Such differences are of three types: differences in the type and degree of punishment, differences in exemption from punishment, and differences in the execution of punishment. Are these differences at odd with individuals' equality before law and, as a result, unjust? The paper tries to answer the question on the basis of rational arguments and familiar principles and concepts in penal law. The research shows there are differences between men and women in cases of adultery, homosexuality, pimping, and apostasy. In addition, there are allowances for women in executing punishments. The paper, finally, elaborates on legal vacuums existing in such cases.