To improve measurement accuracy of blood pressure. A wrist sphygmomanometer comprises a cuff spring formed in a curved shape to fit the semicircle on the side of the pulsation part of the wrist, having a mount portion formed outside a cuff band including the cuff spring as a core material, having an air bag inside, and wound around a wrist and a sphygmomanometer main body mounted on the mount portion of the cuff spring, having a pressure pump for supplying air to the air bag, wherein the cuff spring has a slit formed at an arbitrary position in the axial direction so as to extend in the peripheral direction, and both sides of said slit in the axial direction of said cuff spring are formed having different curvatures with each other.
