PURPOSE: To improve the airtightness and durability, by packing a sealing agent composed of powdered talc calcined at a prescribed temperature in an annular vacant space formed between an oxygen detection element and a main metallic fitting surrounding said element.

CONSTITUTION: A collar 12 is formed on a drum part and an oxygen detection element 1 consisting of a stabilized zirconia with bottomed cylindrical shape which is provided with a small diameter head part 14 upward from this collar 12, is housed in an axis hole 33 of a main metallic fitting, 3 putting losely on the outer diameter face of the collar 12 of the oxygen detection element and is supported directly on a stair-stepped seat 32. Talc calcined in a range of 550W 1,000°C for 24hr is packed in an annular vacant space formed between the hole 33 and the part 14 and this vacant space is sealed by compression after prssurized at 2,500kg. Thus constituted oxygen sensor has superior airtightness and durability at the high temperature.