A hydrogen production process comprising a membrane reactor and a carbon dioxide separator for the steam reforming of methane at 500¡î has been simulated without employing a sweep gas for hydrogen separation, while the one-pass conversion of methane with a membrane reactor is 35% or below. Recycling of the reaction gas increases the apparent conversion of methane, but the conversion is gradually saturated with increasing recycling retio(molar ratio of recycled gas to feed gas) without carbon dioxide separation. Separation of carbon dioxide from the exit gas of the membrane reactor increases the apparent conversion of methane linearly with increasing recycling ratio and 100% conversion can be attained under conditions suitable for industrial operation.