A blood purification system that is capable of notifying any changes in the patient's condition on the basis of noninvasive vital sings of the patient that are observed during the blood purification treatment. An external information-processing apparatus includes an external input device into which a vital sign detected by a detecting device is inputtable in real time； a checking device capable of checking whether or not the vital sign inputted in real time into the external input device satisfies a predetermined condition； and an external output device capable of outputting, if it is determined by the checking device that the vital sign satisfies the predetermined condition, a result of the checking or checked information including the vital sign leading to the result of the checking to a blood purification apparatus. The checked information outputted from the external output device is displayable on a display included in the blood purification apparatus.
