Between a gas sensing layer (4) and a base member (15) composed of a silicon substrate (2) and an insulating coat layer (3), there is formed an adhesion layer 7, to improve the adhesion therebetween, and to prevent separation. The gas sensing layer (4) and sensing electrodes (6) are electrically connected by abutment of a confronting surface (61) of sensing electrodes (6) confronting the gas sensing layer (4) and sides surfaces of the sensing electrodes on both sides, on the gas sensing layer (4), and accordingly the gas sensor properly senses an electric characteristic of the gas sensing layer (4) varied in accordance with a concentration variation of a specified gas. Furthermore, the sensing electrodes (6) are in contact with the gas sensing layer (4), but the sensing electrodes are not in contact with the adhesion layer (7). Therefore, the adhesion layer (7) need not be a complete insulating layer, and it is possible to use, as the adhesion layer, an incomplete insulating film or a conductive film, so that options of the adhesion layer (7) are increased.