PURPOSE: To miniaturize a sensor and to reduce the power consumption by forming a heater layer on one joint surface of a ceramic base body for constituting a substrate by joining two pieces or more, and forming a gas detecting electrode layer and a gas detecting element layer, on the other non-joint surface.

CONSTITUTION: To the tip part 31a of a ceramic substrate 31, a heater layer 32 is printed, and connected to heater electrode layers 33, 34 printed in the same way. Also, gas electrode layers 35, 36 are printed to the substrate 31. To another ceramics substrate 41, gas detecting electrode layers 42, 43 are printed, joined to the substrate 31, thereafter, joint parts 42a, 43a are brought to a through-hole connection to the joint parts 35a, 36a of the electrode layers 35, 36. The substrates 31 and 41 are coupled, thereafter, a reinforcing plate 45 is further coupled onto the substrate 41. Subsequently, an alumina ball (not shown in the figure) is pressed thermally against an exposed tip part 41a a and sintered, and again, sintered after applying titania, by which a gas detecting element layer 2 is formed.