To provide a blood purification system that is capable of efficiently and assuredly 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, with a blood purification apparatus manufacturable at a reduced cost. An external information-processing apparatus 4 includes an external input device 11 into which a vital sign detected by a detecting device 2 is inputtable in real time； a checking device 12 capable of checking whether or not the vital sign inputted in real time into the external input device 11 satisfies a predetermined condition； and an external output device 13 capable of outputting, if it is determined by the checking device 12 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 1. The checked information outputted from the external output device 13 is displayable on a display 5 included in the blood purification apparatus 1.
