According to the present invention, there is provided an extracorporeal circulation apparatus including a blood circuit including an arterial blood circuit and a venous blood circuit whose proximal ends are connected to a blood purifier, the blood circuit allowing a patient's blood to extracorporeally circulate from a distal end of the arterial blood circuit to a distal end of the venous blood circuit； a discharge unit through which a priming solution supplied into the blood circuit is discharged to an outside； a negative-pressure-generating unit that generates a negative pressure in a region of the blood circuit, the region being filled with the priming solution； and a control unit that controls the negative-pressure-generating unit. The control unit executes a priming step in which the priming solution supplied into the blood circuit is discharged through the discharge unit while a flow route in the blood circuit is filled with the priming solution； a negative-pressure-generating step in which, after the priming step, a negative pressure is generated in the region by the negative-pressure-generating unit； and a discharge step in which bubbles in the region subjected to the negative pressure generated in the negative-pressure-generating step are caused to flow and are discharged through the discharge unit.
