The present invention enables making uniform contact with the tragus using inner and outer cuffs, each of said inner and outer cuffs being comprised of a cuff member 40 connected to a duct 4 and a cuff bladder 22 having a body 27 which is fixed onto said cuff member in an air-tight manner and can expand and contract, comprised in such manner in order to carry out accurate blood pressure measurement at any one given point in time without being affected by the pinch width of the tragus and depth to the tragus even with repeated mounting and removal from the ear auricle, and also comprised such that a lid 23 of said cuff bladder forms a pressing surface 25 in a shape of a protrusion.