To provide a differential pressure measuring device capable of replacing a seal diaphragm, reducing the maintenance cost, and friendly to the environment.

This differential pressure measuring device in which a main body storing a pressure sensor is kept in contact with a measured fluid via the seal diaphragm is provided with a seal block insertion hole provided on the measured fluid contact face of the main body, a seal block inserted and fitted into the seal block insertion hole, a seal body provided on the connection face of the seal block and the seal block insertion hole to seal the seal block and the seal block insertion hole, a guide hole provided on the seal block to guide the measured fluid, and the seal diaphragm provided on the connection face of the seal block and the measured fluid contact face to seal the measured fluid contact face and the guide hole guiding the measured fluid.