flat sheet 22 are layered and wound together to form spiral like alternate layers thereby forming a honeycomb shaped metallic catalyst carrier 23 the corrugated sheet 21 and the flat sheet 22 are for example foil materials of a thickness of about 50 u03bcm having a composition of 20 percent chromium 5 percent aluminum and 75 percent iron the surfaces of the corrugated sheet 21 and flat sheet 22 in the nonjoined regions are coated with an insulating film of activated al 2 o 3 on the coating of the activated al 2 o 3 is carried the catalyst precious metal for example platinum palladium or rhodium referring to fig1 and 19 the positive electrode 24 is disposed at the center of the catalyst carrier 23 along its axial direction the positive electrode 24 is connected in a conductive fashion to the catalyst carrier 23 the catalyst carrier 23 is inserted into a metallic cylindrical case 25 and affixed to the case 25 by for example brazing the catalyst carrier 23 is made conductive with the case 25 as shown in fig1 a negative electrode 26 is connected to the side of the case 25 as shown in fig1 the positive electrode 24 extends in the axial direction of the case 25 then is bent in an l shape and extends in the diametrical direction of the case 25 and passes through the side surface of the case 25 the positive electrode 24 is electrically insulated from the case 25 by the insulating material 27 referring to fig1 in the cylindrical region 23a of the center of the catalyst carrier 23 and the cylindrical region 23b hatched region in figure at the outer periphery the mountains and valleys of the corrugated sheet 21 are.