sensor 2 only in the structures of the gas sensing device 204 and gas sensing device 804 and mainly the gas sensing device 804 will be described while description of other components is simplified or omitted fig7 is a sectional view of the detecting portion 608 in the gas sensing device 804 as shown in fig7 the gas sensing device 804 comprises a first base body 601 and a second base body 603 formed on the first base body 601 such that it contains cavity internally then a third base body 620 is disposed in the cavity and the third base body 620 contains a heating element 602 composed of mainly platinum an oxygen concentration detecting cell 800 is comprised of a first solid electrolyte body 605 and a first electrode 604 and second electrode 606 formed on both faces of the first solid electrolyte 605 on the other hand an oxygen pump 900 is comprised of a second solid electrolyte 609 and a third electrode 608 and fourth electrode 610 formed on both faces of the second solid electrolyte 609 a through hole 621 is formed in the second solid electrolyte body 609 such that it goes through in the lamination direction an insulating layer 607 is formed between the oxygen pump cell 900 and the oxygen concentration detecting cell 800 the insulating layer 607 is comprised of an insulating portion 614 and a diffusion rate controlling portion 615 a gas detecting chamber 607 c is formed at a position corresponding to the first electrode 604 and third electrode 608 in the insulating portion 614 of the insulating.