The invention also simplifies the structure of the gas detection sensor as well as H ₂ O or O a subject to be detected to detect with high accuracy the concentration of oxygen gas in the gas in the presence of ₂ containing a concentration or the combustible gas of the combustible gas in the detected gas that would be to ensure that the primary purpose. In order to achieve the above object, in the gas detection sensor of the present invention, so as to originate a detection signal of the combustible gas by the heating of the sensor by contact reaction of the combustible gas, the platinum coating film on the gas contact surfaces to the detected gas into contact retention diaphragm and a first sensor to gas ratio contact surface of the diaphragm is made of a thermocouple fixed by two kinds of one-up the side of each of the dissimilar metal, which is heated by the contact reaction of the combustible gas, the detected gas into contact is the gas ratio and the contact surface of the diaphragm, the diaphragm having a gas contacting surface composed of a thermocouple fixed by two kinds of one-side-up to each of a different metal, consists of a second detection sensor for detecting a temperature of the detected gas.