PURPOSE: To prevent the generation of air bubbles in the blood flowing in a blood storage part, by providing hydrophylicity to the surface of a blood flow passage at least a part of which is inclined.

CONSTITUTION: In an oxygenator apparatus wherein a blood storage tank 1 is integrated with an oxygenator 11 and a heat exchanger, blood receiving the supply of oxygen flows out from the blood outflow port 22 of the oxygenator 11 to flow in the blood storage tank 1 communicating with the oxygenator 11 from the blood introducing port 2 thereof and reaches a blood inflow part 5 to be sent along the surface of a blood flow passage 4 and is stored in a blood storage part 6. At this time, the surface of the blood flow passage 4 of the blood storage tank 1 is made hydrophylic and the wettability thereof with blood and a priming liquid is enhanced to form homogenous flow as a whole. As a result, air bubbles are not generated in blood.