A sphygmomanometer includes: a bag-shaped sensing cuff to be worn to wrap a measurement site; a back plate disposed on the sensing cuff along a surface opposite to the measurement site; a pressing member for pressing the back plate toward the measurement site; and a blood-pressure calculating part calculating a blood pressure based on a pressure of a fluid stored in the sensing cuff. Regarding a longitudinal direction perpendicular to a circumferential direction of the measurement site to be wrapped by the sensing cuff, a surface facing the measurement site in edge potions on both sides in a width direction along the longitudinal direction of the back plate is curved in a direction away from the measurement site toward tips.