An extracorporeal blood circulation system reduces the risk of generation of air bubbles entering the circulation circuit associated with placement of a pressure sensor that detects a patient's blood pressure at a blood removal line. Instead of directly measuring pressure at the blood removal line where suction exists, an intermediate part pressure sensor detects pressure between a centrifugal pump and an oxygenator. A controller identifies a discharge pressure specific to the centrifugal pump based on a rotation speed of the pump and a blood flow rate. The discharge pressure and the intermediate pressure values are combined to estimate the pressure at the blood removal line.
