This article investigates the effect of human capital on social capital. The ‎sample includes the employees of National Petrochemical Company and the ‎required data were collected by questionnaire. Trust, civil participation and ‎leadership, voluntariness, informal social relations and diversity in friendship ‎were considered for measuring social capital. Also experience, education, ‎creativity, skill and health were used to measure human capital. The results ‎showed that social capital will be increased by investment on human capital, ‎and one of the best ways to achieve that, is investment on education because it ‎has great effect on all factors of social capital. ‎