A blood purification system comprising: a blood purification apparatus configured to perform blood purification treatment in which blood of a patient that is extracorporeally circulated is purified, the apparatus including a display configured to display information on the blood purification treatment in real time; a detecting device configured to detect non-invasively and in real time a vital sign of the patient during the blood purification treatment; and an external information-processing apparatus configured to receive and monitor in real time the vital sign detected by the detecting device, wherein the external information-processing apparatus includes an external input device into which the vital sign detected by the detecting device is inputtable in real time; a checking device configured to check whether or not the vital sign inputted in real time into the external input device satisfies a predetermined condition; and an external output device configured to output, 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 the blood purification apparatus, wherein the checked information outputted from the external output device is inputted into an input device of the blood purification apparatus and displayable on the display included in the blood purification apparatus, wherein the checking device is configured to check whether or not the vital sign inputted in real time is abnormal, and the result of the checking that is determined to be abnormal or the checked information including the vital sign leading to the result of the checking is outputted from the external output device and inputted into the input device of the blood purification apparatus, and wherein the blood purification apparatus is configured so that, when any checked information that is determined to be abnormal is inputted into the input device, information regarding the blood purification treatment is displayed on the display, which information comprises the rate of change in the circulating blood volume ΔBV as a chart β and/or the normalized dialysis dose Kt/V as a chart y, and a chart α is superposed on the information regarding the blood purification treatment, which chart α indicates that the checked information that is determined to be abnormal is inputted. a blood purification apparatus configured to perform blood purification treatment in which blood of a patient that is extracorporeally circulated is purified, the apparatus including a display configured to display information on the blood purification treatment in real time; a detecting device configured to detect non-invasively and in real time a vital sign of the patient during the blood purification treatment; and an external information-processing apparatus configured to receive and monitor in real time the vital sign detected by the detecting device, wherein the external information-processing apparatus includes an external input device into which the vital sign detected by the detecting device is inputtable in real time; a checking device configured to check whether or not the vital sign inputted in real time into the external input device satisfies a predetermined condition; and an external output device configured to output, 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 the blood purification apparatus, an external input device into which the vital sign detected by the detecting device is inputtable in real time; a checking device configured to check whether or not the vital sign inputted in real time into the external input device satisfies a predetermined condition; and an external output device configured to output, 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 the blood purification apparatus, wherein the checked information outputted from the external output device is inputted into an input device of the blood purification apparatus and displayable on the display included in the blood purification apparatus, wherein the checking device is configured to check whether or not the vital sign inputted in real time is abnormal, and the result of the checking that is determined to be abnormal or the checked information including the vital sign leading to the result of the checking is outputted from the external output device and inputted into the input device of the blood purification apparatus, and wherein the blood purification apparatus is configured so that, when any checked information that is determined to be abnormal is inputted into the input device, information regarding the blood purification treatment is displayed on the display, which information comprises the rate of change in the circulating blood volume ΔBV as a chart β and/or the normalized dialysis dose Kt/V as a chart y, and a chart α is superposed on the information regarding the blood purification treatment, which chart α indicates that the checked information that is determined to be abnormal is inputted.