NOVELTY - The generator for generating hydrogen using steam reforming, comprises a unit (1) for desulfurizing a hydrocarbon feed, a reformer (2) for performing a steam-reforming reaction by mixing the desulfurized hydrocarbon feed with a water feed and then heating the mixture using a burner (5) to form a reformed gas, a water gas converter (3) for converting carbon monoxide in the reformed gas obtained from the reformer into a converted gas of hydrogen and carbon dioxide, a pressure swing absorption (PSA) unit (4) for separating hydrogen from the converted gas, and a first heat exchanger.    USE - The generator is useful for generating hydrogen using steam reforming, where the hydrogen is useful in a fuel cell system for an automobile, household and distributed electric generation.    ADVANTAGE - The hydrogen generator has easy start-up, stable operation without requiring additional apparatus or costs, high thermal efficiency and high durability, and avoids the problems related to safety verification and power loss.    DETAILED DESCRIPTION - The generator for generating hydrogen using steam reforming, comprises a unit (1) for desulfurizing a hydrocarbon feed, a reformer (2) for performing a steam-reforming reaction by mixing the desulfurized hydrocarbon feed with a water feed and then heating the mixture using a burner (5) to form a reformed gas, a water gas converter (3) for converting carbon monoxide in the reformed gas obtained from the reformer into a converted gas of hydrogen and carbon dioxide, a pressure swing absorption (PSA) unit (4) for separating hydrogen from the converted gas, a first heat exchanger for superheating the water feed to an evaporation temperature of water, a second heat exchanger for preheating the mixture of the desulfurized hydrocarbon feed and superheated water using the reformed gas discharged from the reformer, a third heat exchanger for decreasing a temperature of the reformed gas using external air before the reformed gas is introduced into the water gas converter, and a fourth heat exchanger for additionally decreasing a temperature of the gas discharged from the water gas converter using tap water before the converted gas is introduced into the PSA unit. The water feed is superheated using the exhaust gas discharged from the burner before the water feed is mixed with the desulfurized hydrocarbons. The hydrocarbon feed, the air heated by the heat exchange between the reformed gas and the air in the third heat exchanger, and the residual gas are used as fuel of the burner. Each of the first, second, third and fourth heat exchanger is a finned tube type heat exchanger or a shell and tube type heat exchanger. A bypass line (6) is arranged for controlling an amount of air introduced into the third heat exchanger to set a temperature of the reformed gas at an inlet of the water gas converter to 180-200 degrees C. The hydrocarbon feed includes gaseous or liquid hydrocarbons including liquefied natural gas, liquid petroleum gas, naphtha, gasoline and kerosene. An INDEPENDENT CLAIM is included for a method of operating the steam-reforming hydrogen generator.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic block diagram of a hydrogen generator.    Desulfurizer (1)    Reformer (2)    Water gas converter (3)    Pressure swing absorption unit (4)    Burner (5)    Bypass line. (6)