PURPOSE: To improve accuracy in measurement and to make negligible the floating capacity between two electrodes by forming a support and a diaphragm (including a base plate) of fused quartz, quartz crystal, glass, ceramics, sapphire, etc. and providing an adhesive layer and a supporting part between the two electrodes which are formed into a concentrical shape.

CONSTITUTION: An electrode support 21 consists of a material such as, for example, fused quartz, quartz crystal, glass, ceramics, sapphire, or the like, and two concentrical electrodes 22, 24 are formed on the surface thereof. These electrodes 22, 24 are formed by vapor deposition, etc. in the prescribed depth position of the support. A measuring diaphragm 26 consists of the material similar to the material of the support 21, and a prescribed metal is deposited by a means such as vapor deposition over the entire surface of the diaphragm facing the support 21, by which an electrode 23 is formed. The support 21 and the diaphragm 26 are joined by an adhesive layer 25 such as low melting glass, glass, org. adhesive agent, metal or the like in such a way that the electrodes face each other.