Carbon dioxide (CO₂) emission resulting from using fossil-fuel has been steadily increased. Hydrogen has attracted an attention as a clean energy resource, since it is combusted without generating CO₂. A steam methane reforming (CH₄ + 2H₂O → 4H₂ + CO₂, SMR) has been the most commercialized process for producing hydrogen from low-cost methane. However, more than 10 kg of CO₂ is generated to produce 1 kg of hydrogen. Methane decomposition (CH₄ → 2H₂ + C) can be an alternative to SMR, because molecular hydrogen and solid carbon are produced through the decomposition reaction. In this work, methane was pyrolyzed in the bubble column filled with a molten transition metal halide to produce hydrogen and separable carbon. A strong C-H bond of methane was activated on the interface between gas and melt to form CHx radicals. Various hydrocarbon intermediates were subsequently generated by combing CHx radicals. Then, hydrogen and separable carbon were produced by pyrolyzing hydrocarbon intermediates. In the bubble column reactor, the surface of the melt was continuously regenerated and the solid carbon cannot be immobilized. Therefore, there was no catalytic deactivation for methane pyrolysis in the melt system. Molten transition metal halides such as manganese chlorides and iron chlorides were used as active catalysts for methane pyrolysis. An apparent activation energy of a molten transition metal halide was measure as around 200 kJ/mole for methane decomposition, which was much lower than that of gas-phase reaction (about 400 kJ/mole). The solid carbon produced from a molten transition metal halide was highly graphitic, suggesting its potential usage for commercial applications.