PURPOSE: To suppress the poisoning of the catalyst layer on an outside surface side by lead and to improve oxidation function by forming a protective layer of γ-alumina mixed with catalyst particles.

CONSTITUTION: The catalyst layer 14 is formed by depositing an inside electrode 12 and outside electrode 13 consisting respectively of platinum to part of the inside surface and outside surface of a ceramic pipe 11 consisting essentially of zirconium oxide and having a closed end and depositing further platinum by evaporation on the outside surface side. The protective layer 15 covering the catalyst layer 14 is formed of the γ-alumina mixed with, for example, platinum (Pt) particles. The lead component contained in exhaust gas is thereby adsorbed to the γ-alumina having a large specific surface area, by which the poisoning of the catalyst layer 14 by the lead is suppressed when a leaded gasoline is used as fuel for an engine. Since the platinum particles 16 in the γ-alumina accelerates the oxidation of CO, the influence of the poisoning of the catalyst layer 14 is suppressed.