Background and aims: Burden of HIV and AIDS is considerably different among regions and countries around the world. The aim of this study was to assess the inequality in the prevalence of HIV, according to human development index worldwide. Methods: The desired outcome was prevalence of HIV, which was estimated in 100 countries in 2012. The annual report of Joint United Nations Programme on HIV and AIDS (UNAIDS) was used for determining the prevalence of HIV in countries. In addition, we used the data of the human development index of the countries from United Nations Development Programme (UNDP). We defined inequality of human development index in the prevalence of HIV by using the concentration index. Results: Concentration index for prevalence of HIV among 25-49 years adults was -0.217 (95% CI: -0.074, -0.361). This index indicated the inequality in the prevalence of HIV based on the human development index and concentrating on more HIV subjects in poor countries. In addition, concentration indexes in the prevalence of HIV among young males and females were 0.229 and -0.200, respectively. Conclusion: This study emphasized on the inequality in the prevalence of HIV and concentration of HIV in countries with lower human development index. Therefore, it is recommended that the international organizations should perform fundamental actions to help these countries, such as prevention, care and treatment programs.