An apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, including a first blood-pressure measuring device which measures a first blood pressure of a right inferior limb of the subject, a second blood-pressure measuring device which measures a second blood pressure of a left inferior limb of the subject, a third blood-pressure measuring device which measures a third blood pressure of a superior limb of the subject, a first information obtaining device which obtains first information relating to a first velocity of propagation of a first pulse wave which propagates through a first route a portion of which runs in the right inferior limb, a second information obtaining device which obtains second information relating to a second velocity of propagation of a second pulse wave which propagates through a second route a portion of which runs in the left inferior limb, a selecting device for selecting one of the measured first and second blood pressures that corresponds to one of the first and second information that relates to a lower one of the first and second velocities, and an index determining device for determining the superior-and-inferior-limb blood-pressure index, based on the selected one of the first and second blood pressures, and the measured third blood pressure.