An apparatus for measuring a superior-and-inferior-limb blood-pressure (“BP”) index of a living subject, including an inferior-limb BP measuring device which includes a first inflatable cuff adapted to be wound around an inferior limb of the subject and which measures an inferior-limb BP value of the subject based on a first pulse wave obtained while a first pressure of the first cuff is changed, a superior-limb BP measuring device which includes a second inflatable cuff adapted to be wound around a superior limb of the subject and which measures a superior-limb BP value of the subject based on a second pulse wave obtained while a second pressure of the second cuff is changed, a cuff-pressure changing device which changes the first and second pressures of the first and second cuffs, such that a time when the first pressure being changed becomes equal to an estimated inferior-limb BP value coincides with a time when the second pressure being changed becomes equal to an estimated superior-limb BP value, and an index determining device for determining the BP index of the subject, based on the inferior-limb and superior-limb BP values measured by the inferior-limb and superior-limb BP measuring devices while the first and second pressures of the first and second cuffs are changed by the cuff-pressure changing device.