A sphygmomanometer device includes a piezoelectric pump, a valve, and a cuff. The valve includes a first valve housing, a diaphragm, and a second valve housing. The diaphragm is fixed to the second valve housing and first valve housing such that it is separated from a valve seat and the periphery of an opening portion in the diaphragm is in contact with a valve seat while providing a pressure thereto. Thus, the diaphragm defines a lower valve chamber communicating with a first vent hole, an upper valve chamber communicating with a second vent hole, a lower valve chamber communicating with a first vent hole, and an upper valve chamber communicating with the upper valve chamber, together with the second valve housing and first valve housing.
