A blood purification apparatus is provided in which parameters related to ultrafiltration can be changed assuredly and smoothly at the restart of blood purification treatment suspended with the release of the patient from a blood circuit during the blood purification treatment. A blood purification apparatus 1 in which the blood purification treatment that is suspended with a release of the patient from a blood circuit 2 during the blood purification treatment is restartable includes a calculating device 13 capable of calculating a variable amount related to a patient's body weight that changes with the suspension and restart of the blood purification treatment； and a changing device 14 capable of changing, in accordance with the variable amount calculated by the calculating device 13, a parameter related to ultrafiltration that is set by a setting device 11.
