PURPOSE: To enhance the sensor reliability and facilitate the sensor fixing operation by clamping the sensor element by fixing pieces and contacting the electrode contact portions extending from the fixing pieces with electrodes.

CONSTITUTION: When a sensor element 1 is inserted between fixing pieces 8 while the sides 7 thereof are slid thereagainst, the fixing pieces 8 are gradually elastically deformed in directions in which they are diverged from a base 6 as a fulcrum. And the sensor element 1 is inserted between electrode contact portions 10 while these contact portions 10 are also elastically deformed in the divergence direction in such a manner as to clamp the sensor element 1 between both 10 in the thicknesswise direction thereof. Subsequently, the sensor element 1 is further inserted between the fixing pieces 8 and the sides 7 thereof are fitted into fixing holes 9. Therefore, the element l is reliably fixed by the fixing pieces 8 while, on the other hand, the contact portions 10 contact their respective relevant electrodes 2 while clamping the element 1 from both sides thereof. As mentioned above, this arrangement can prevent the occurrence of defective sensing or the like resulting from the soldering performed with respect to the electrodes, thereby enhancing the reiiability of the sensor, facilitating the performance of the sensor fixing/connecting operations, and reducing the number of the required operational steps.