The apparatus for blood flow control in an extracorporeal circuit comprises: a user interface for setting a desired blood flow value (qbREAL) and a datum relating to the vascular access, a memory for recording a plurality of mathematical relations having mathematical expressions relating to the vascular access organ to be used, and a control unit. The control unit identifies the vascular access, selects, from among the plurality of mathematical relations present in the memory, a relation which corresponds to the vascular access identified, and calculates, as a mathematical function of the set value for the desired flow (qbREAL), a value at which to set the angular velocity of the pump associated to the extracorporeal circuit and/or a theoretical value of the arterial pressure upstream of the pump.