PURPOSE: To obtain a damper which can eliminate the influence of a dynamically changing pressure on a pressure measuring device for monitoring pressure at the time of measuring the blood pressure, etc.

CONSTITUTION: A damper for pressure measuring instrument is incorporated in a valve body. A fluid passage 6 communicates with a first division chamber 9 closed with an elastic rubber diaphragm 10. One side face of the diaphragm 10 on the opposite side of the chamber 9 forms a second division chamber 13 which is in contact with the atmosphere through an opening 14 formed to provide a fluid resistance. The fluid resistance exhibits a damper effect.