An extracorporeal blood circulator includes a control unit and a speed manipulation section. A rotation display section displays a lower limit rotation setting value of a pump motor in accordance with a command of the control unit. The lower limit rotation speed setting value is a minimum rotation speed for preventing backflow of blood inside a circulation circuit A manually adjusted speed setting request from the manipulation section controls the pump speed, except that the controller enforces the lower limit speed setting unless receiving confirmation from a manipulator.
