NOVELTY - The fuel improver consists of reforming chamber (36) equipped with modification catalyst layers (38,40). The reforming chamber is connected to combustion chamber (46). The fuel supplied by injector (48) is lighted up by glow plug (49) to produce combustion gas. When the improver is started, the combustion gas from chamber (46) is directly supplied to catalyst layer.    USE - For reforming the gas containing hydrocarbon.    ADVANTAGE - Since combustion gas is directly supplies to modification catalyst layer, catalyst layer is heated up quickly and easily and passing of hot gas is done only once hence the time required for heating is less. Since CO sensor is provided, reformed gas is obtained efficiently and reliably. Since the improver is controlled, firing of combustion chamber is secured and durable heat for firing is raised effectively. By providing gas outlet sensor, various unnecessary sensors are eliminated and hence the process is economical.    DETAILED DESCRIPTION - The fuel improver consists of a detection unit for detecting the voltage of plug for fixing. When the detected value reaches the set point, fuel for heat is injected into the combustion chamber. A timer provided to plug, allows the passage of fuel to combustion chamber only for specific period. A temperature sensor (51) is provided for detecting the temperature of combustion chamber. When the temperature in temperature sensor reaches a set value, the electricity for plug firing is stopped. The reformed gas from the reform chamber is supplied to fuel battery through a valve. The reformed gas is supplied to catalyzed combustion device by a by-pass flow path. A temperature sensor provided to modification catalyst detects the reformed gas outlet temperature. The amount of heat supplied to the reforming chamber is based on the temperature detected by sensor. A CO sensor is provided in reforming portion for detecting the concentration of CO or residual hydrocarbon. An INDEPENDENT CLAIM is also included for control method of fuel improver, involves supplying fuel, water vapor and oxygen for modification catalyst. The catalyst layers are heated to predetermined temperature by the heat of fuel supplied from combustion chamber. The reform gas is produced by the simultaneous oxidation and modification reactions. The reform gas and H2O is supplied to combustor, evaporator when the temperature of evaporator reaches a predetermined value.    DESCRIPTION OF DRAWING(S) - The figure shows the longitudinal cross-sectional diagram of fuel improver.    Reforming chamber; (36)    Modification catalyst layers; (38,40)    Combustion chamber; (46)    Injector; (48)    Glow plug; (49)    Temperature sensor (51)