PURPOSE: To provide the titled apparatus having low operation cost, by placing a tubular ceramic heater containing a heating element in front of a reforming catalyst, thereby achieving almost uniform heating of the mixed gas and the reduction of the power consumption for heating.

CONSTITUTION: A ceramic heater 5 having a number of perforations 6 and containing a heating element 9 therein is used in the titled apparatus. Concretely, a plural number of reforming catalyst rods 2 having a number of pores 3 and separated from each other with heat-insulating ceramic paper sheets 4 are inserted in the reaction tube 1 covered with a heat-insulating material 10, and a number of the above ceramic heaters 5 are supported with the supporting plate 7 in front (i.e. upstream) of the catalyst. A high efficiency hydrocarbon fuel reformer for reacting hydrocarbons with water (or air) to obtain inorganic gas composed mainly of hydrogen and carbon oxide gases can be constructed by this method.