An apparatus for measuring a superior-and-inferior-limb blood-pressure index of a living subject, including a first measuring device which measures a first blood pressure of an inferior limb; a second measuring device which measures a second blood pressure of a superior limb; an information obtaining device for iteratively obtaining information changing in relation with change of blood pressure of the subject; a change-value determining device for determining a change value of blood pressure of the subject between a first time when the first blood pressure is measured and a second time when the second blood pressure is measured, based on a first piece of information obtained by the information obtaining device at the first time and a second piece of information obtained by the information obtaining device at the second time; a corrected-blood-pressure determining device for determining, based on the determined change value, one of the first and second blood pressures to a corrected blood pressure that would have been measured at one of the first and second times that corresponds to the other of the first and second blood pressures; and an index determining device for determining the superior-and-inferior-limb blood-pressure index, based on the determined corrected blood pressure and the other of the first and second blood pressures that has not been corrected by the corrected-blood-pressure determining device.