NOVELTY - Mixed raw material of hydrocarbon group raw material (M) is heated and vaporized. Material (M) is modified. Liquid component in the reformed gas is removed and discharged as drain water. Unwanted component (U) in reformed gas is adsorbed to adsorption agent. Hydrogen enriched gas is derived from adsorption tower. Off gas containing hydrogen and component (U) are emitted. Off gas is burnt during vaporization. Produced combustion gas is used as heat source for heating. Drain water is evaporated by combustion gas. Thus, hydrogen production drain water is processed.    USE - For processing of drain water of hydrogen production.    ADVANTAGE - The method enables efficient processing of drain water of hydrogen production.    DETAILED DESCRIPTION - Mixed raw material containing hydrocarbon group raw material is heated and vaporized. The hydrocarbon group raw material in the vaporized material is modified to produce reformed gas containing hydrogen gas. Liquid component mixed in the reformed gas is separated, removed and discharged as drain water. The reformed gas after vapor-liquid separation process is introduced into an adsorption tower and unwanted component in the reformed gas is made to adsorb to adsorption agent filled in the adsorption tower by pressure-fluctuation adsorption type gas separation method. Hydrogen enriched gas is derived from the adsorption tower and unwanted component is desorbed from the adsorption agent. The off gas containing hydrogen remaining in the adsorption tower and unwanted component are discharged. The off gas discharged from the adsorption tower is burnt during vaporization of raw material. The produced combustion gas is used as heat source for heating of the mixed raw material. The drain water discharged through vapor-liquid separation process is evaporated by using the combustion gas after heating of mixed raw material as heat source. Thus, the drain water of hydrogen production is processed. An INDEPENDENT CLAIM is included for hydrogen production system (X1).    DESCRIPTION OF DRAWING(S) - The figure shows the schematic block diagram of hydrogen production system. (Drawing includes non-English language text)    Vaporizer (1)    Modifier (2)    Heat exchanger (3)    Vapor-liquid separator (4)    Drain water treatment device (6)    Hydrogen production system (X1)