NOVELTY - The oxidation self thermal type reformer (1) has reforming layer (2) and oxidation exothermic layer (3). Layer (2) has at least a portion filled with a reforming catalyst to which mixture of hydrocarbon or aliphatic alcohol and steam is contacted to obtain reformed gas having hydrogen. Layer (3) has at least portion filled with oxidation catalyst for oxidizing portion of reformed gas to form heat. Reformer has inner reforming layer (2A), oxidation exothermic layer (3) and outer reforming layer (2B). Portion(s) of catalyst in reforming layers contains ruthenium metal.    USE - For oxidation self thermal reforming (claimed) and producing reformed gas used as fuel for solid oxide fuel cell.    ADVANTAGE - The oxidation self thermal type reformer utilizes heat of combustion for modification reaction within apparatus.    DETAILED DESCRIPTION - The oxidation self thermal type reformer (1) has a reforming layer (2) and an oxidation exothermic layer (3). The reforming layer has at least a portion filled with a reforming catalyst to which mixture of hydrocarbon or aliphatic alcohol and steam is contacted to obtain reformed gas containing hydrogen by reforming reaction. The exothermic layer has at least a portion filled with an oxidation catalyst for oxidizing portion of reformed gas to produce heat. The reforming layer is arranged on upstream of oxidation exothermic layer. The reforming layer and exothermic layer are cylindrical. The reformer has triple circular tube structure comprising inner reforming layer (2A), oxidation exothermic layer (3) and outer reforming layer (2B) disposed sequentially from radial direction. At least one portion of reforming catalyst contained in reforming layers contains ruthenium metal. The exothermic layer is filled with mixture of oxidation catalyst and modification catalyst, mixture of oxidation catalyst and heat transfer particle, or mixture of oxidation catalyst, modification and heat transfer particle. The modification catalyst contains nickel metal and/or rhodium metal.    DESCRIPTION OF DRAWING(S) - The figure shows the sectional view of oxidation self thermal type reformer.    Oxidation self thermal type reformer (1)    Reforming layers (2,2A,2B)    Oxidation exothermic layer (3)    Inner cylinder (4)    Outer cylinder (5)