A blood purification apparatus comprising: a blood circuit through which blood of a patient is allowed to extracorporeally circulate; a blood purifier for giving blood purification treatment by purifying the blood of the patient that extracorporeally circulates through the blood circuit ; an ultrafiltration device capable of performing ultrafiltration for removing water from liquid in the blood circuit ; an infusion device (L8) capable of performing fluid infusion or blood return by introducing liquid into the blood circuit ; a setting device capable of setting a parameter related to ultrafiltration performed by the ultrafiltration device ; and a control device that controls the ultrafiltration device in accordance with the parameter that is set by the setting device , wherein the blood purification treatment that is suspended with a release of the patient from the blood circuit during the blood purification treatment is restartable, wherein the blood purification apparatus further includes a calculating device capable of calculating a variable amount related to the patient's body weight that changes with the suspension and restart of the blood purification treatment; a changing device capable of changing, in accordance with the variable amount calculated by the calculating device , the parameter related to ultrafiltration that is set by the setting device ; and a display (M), wherein the blood purification apparatus is configured such that a plurality of variable amounts related to the patient's body weight that changes with the suspension and restart of the blood purification treatment are displayable on one particular screen of the display (M). a blood circuit through which blood of a patient is allowed to extracorporeally circulate; a blood purifier for giving blood purification treatment by purifying the blood of the patient that extracorporeally circulates through the blood circuit ; an ultrafiltration device capable of performing ultrafiltration for removing water from liquid in the blood circuit ; an infusion device (L8) capable of performing fluid infusion or blood return by introducing liquid into the blood circuit ; a setting device capable of setting a parameter related to ultrafiltration performed by the ultrafiltration device ; and a control device that controls the ultrafiltration device in accordance with the parameter that is set by the setting device , wherein the blood purification treatment that is suspended with a release of the patient from the blood circuit during the blood purification treatment is restartable, wherein the blood purification apparatus further includes a calculating device capable of calculating a variable amount related to the patient's body weight that changes with the suspension and restart of the blood purification treatment; a changing device capable of changing, in accordance with the variable amount calculated by the calculating device , the parameter related to ultrafiltration that is set by the setting device ; and a display (M), wherein the blood purification apparatus is configured such that a plurality of variable amounts related to the patient's body weight that changes with the suspension and restart of the blood purification treatment are displayable on one particular screen of the display (M). <EOS>