A solid pole oxygen sensor having a solid pole, in which one end of a lead wire of platinum or platinum rhodium is buried, tightly covered by a solid electrolyte and pressure-molded into a circular plate, which is dried and then fired in a reducing atmosphere. The surface of a sintered mass thus obtained is plated or baked to form a platinum electrode, and the oxygen sensor element thus obtained is secured by a bonding agent to the tip of a cylindrical ceramic insulator having electroconductive zones to be connected to the platinum electrode in such a manner that the circular face of the circular plate-shaped oxygen sensor element is in contact with the tip surface of the cylindrical ceramic insulator.