An electrically heated catalytic converter for purifying exhaust gas, the electrically heated catalytic converter comprising: a catalyst carrier supporting a catalyst and configured to generate heat by energization; a case for accommodating the catalyst carrier; and an electrical insulation mat interposed between the catalyst carrier and the case, wherein the case comprises an outer tube disposed at the outermost side and an inner tube disposed inside the outer tube; in a cross section upstream of the catalyst carrier taken along a plane including the central axis of the case, the inner tube comprises one or more curvature sections curved so as to outwardly project and extended sections connected to the one or more curvature sections, an insulation layer comprising an amorphous inorganic material is formed at least on an inner surface of the one or more curvature sections and the extended sections of the inner tube, the one or more curvature sections comprise a first curvature section (34a 1) located closest to the catalyst carrier, the first curvature section (34a 1) has a first curvature section insulation layer (36a 1) formed thereon, the first curvature section insulation layer (36a 1) having a thickness of 100 to 400 μm, the extended sections comprise a first extended section (34b 1) connected to the first curvature section (34a 1) and adjacent to the catalyst carrier, the first extended section (34b 1) has a first extended section insulation layer (36b 1) formed thereon, characterized in that the thickness of the first curvature section insulation layer (36a 1) is greater than 1 time to less than 1.4 times the thickness of the first extended section insulation layer (36b 1) and a portion of the surface of the inner tube where the insulation layer is to be formed is roughened. a catalyst carrier supporting a catalyst and configured to generate heat by energization; a case for accommodating the catalyst carrier; and an electrical insulation mat interposed between the catalyst carrier and the case, wherein the case comprises an outer tube disposed at the outermost side and an inner tube disposed inside the outer tube; in a cross section upstream of the catalyst carrier taken along a plane including the central axis of the case, the inner tube comprises one or more curvature sections curved so as to outwardly project and extended sections connected to the one or more curvature sections, an insulation layer comprising an amorphous inorganic material is formed at least on an inner surface of the one or more curvature sections and the extended sections of the inner tube, the one or more curvature sections comprise a first curvature section (34a 1) located closest to the catalyst carrier, the first curvature section (34a 1) has a first curvature section insulation layer (36a 1) formed thereon, the first curvature section insulation layer (36a 1) having a thickness of 100 to 400 μm, the extended sections comprise a first extended section (34b 1) connected to the first curvature section (34a 1) and adjacent to the catalyst carrier, the first extended section (34b 1) has a first extended section insulation layer (36b 1) formed thereon, characterized in that the thickness of the first curvature section insulation layer (36a 1) is greater than 1 time to less than 1.4 times the thickness of the first extended section insulation layer (36b 1) and a portion of the surface of the inner tube where the insulation layer is to be formed is roughened.