Steam gasification of activated carbon or solid carbon residues, derived from pyrolysis of Japanese cedar or particle board, was carried out in the presence of various molten carbonates or eutectic mixtures of them at 973K and 3.0 MPa. Hydrogen and carbon dioxide were produced mainly. Methane and carbon oxide were detected as a trace product. Yield of hydrogen increased significantly in the presence of the molten carbonates. Effects of molten carbonates for the rate of hydrogen formation were following order, Na_2CO_3/K_2CO_3/Li_2CO_3 (60/20/20) > Li_2CO_3/K_2CO_3 (50/50) > K_2CO_3 (100) > Li_2CO_3/Na2_CO_3 (50/50) >Na_2CO_3 (100) > none. These experimental results show that content of the carbonate and physical contact with solid carbon, molten carbonate, and steam is very important for hydrogen production.