PURPOSE: To provide a pressure sensor which can detect a pressure with high accuracy and can maintain the accuracy even under severe despite of having a simple constitution, being easily manufactured, and being low in cost usage surroundings.

CONSTITUTION: An atmosphere-side opening part 8A at an atmosphere communication passage 8 is opened at an internal space 7A which is surrounded by a connector part 7 for a pressure sensor 1 and by a connector on the side of an external apparatus or the like. Then, the opening part 8A which is used to adjust the pressure inside a reference pressure chamber 3 is made to communicate with the atmosphere by utilizing the breathability at the inside of the coating part of an interconnection connected to the external apparatus or the like. Although the constitution of the pressure sensor is simple, the pressure inside the reference pressure chamber 3 can be adjusted surely, and the pressure detection accuracy of the pressure sensor can be maintained to be high even under severe usage surroundings.