PURPOSE: To obtain a strong auxiliary circulation means easy in execution by connecting a balloon driving device and a blood pump to the branch pipe provided to the rear end part of a cannula.

CONSTITUTION: A cannula 1 is formed from a flexible tube having a double lumen structure having a main lumen 2 piercing in the longitudinal direction thereof and a sub-lumen 3 sealed at its leading end and the balloon 4 mounted to the outer periphery of the tube in a hermetically closed state. A plurality of opening parts 5 from the sub-lumen to the chamber of the ballon 4 are formed to the main lumen 2 and driving gas is supplied into the chamber of the balloon 4 through the sub-lumen 3. The main lumen 2 and the sub-lumen 3 are separated at the base part of the cannula 1 and the main lumen 2 is connected to a blood pump 10 while the sub-lumen 3 is connected to a balloon driver 11. If necessary, a pressure measuring and medical fluid injecting sub- lumen 7 is provided to the cannula 1 and the measurement of pressure and the injection of a medical fluid are changed over by the passage change-over cock 12 provided to the base part of the cannula 1.