Catalytic activities of rubber-grade, color and conductive carbon blacks in ethane decomposition for CO2-free hydrogen production were investigated. The ethane decomposition was carried out in a conventional fixed bed reactor under atmospheric pressure at 973 – 1173 K for 2 hours. When the decomposition in the presence of carbon black was compared with the non-catalytic thermal decomposition, the former exhibited significantly higher ethane conversion, higher C(s) selectivity and lower ethylene selectivity with small increase of methane selectivity, which resulted in higher hydrogen yield. This indicates that carbon black is catalytically effective for dehydrogenation of ethane to ethylene as well as subsequent decomposition of ethylene. Among the carbon blacks investigated, fluffy N-330 showed the highest catalytic activity. All the carbon blacks exhibited stable catalytic activity with time. In durability test, a conductive black (BP-2000) maintained its activity for 36 hours. Changes of surface morphology of the carbon blacks with increasing time or temperature were observed by transmission electron microscope and scanning electron microscope. The mechanisms of non-catalytic thermal decomposition and catalytic decomposition were proposed from the analyzed results.