PURPOSE: To obtain a small-sized pressure sensor which does not require piping and compensation and has high resistance against external force, by detecting the spark discharge generated within a pair of electrodes.

CONSTITUTION: A pair of electrodes 14 are opposed through a space and fixed on an insulating board 12 tightly. Fixing holes 16 are penetrated into both ends of the insulating board 12 and prepared for fixing the pressure sensor in the inside of the vessel to be measured. The insulating board 12 is made of rigid electric insulating material. The elctrodes 14 are made of copper as an electrical conductive material, and holes 18 are penetrated into the external end parts of the electrodes 14. High voltage is applied to the electrodes 14 through the holes 18. If a voltage is applied between electrodes 14 and 14 and spark discharging current generated at the time is detected, therefore the change of the pressure at the position where the electrodes 14 and 14 are set can be detected.