A new membrane oxygenator combined with a reciprocating pump was designed to shorten the extracorporeal circulation circuit and to increase the efficiency of oxygenation. At a polycarbonate cylinder, 1700 silicone tubes were bundled and packed among elastic silicone filler. In both inflow and outflow sides of the cylinder, ball valves were equipped. The total available area of the membrane was 8.8×10-2 m2. The membrane was pneumatically driven with a reciprocating pump in performance tests, in which 100% oxygen circulated in the gas side. The mock test shows that the partial pressure of oxygen increases from 1.57×104 Pa at the inlet to 4.72× 104 Pa at the outlet of the oxygenator when 2.0×10-7 m3s-1 saline solution is pumped. The performance has been maintained in animal tests.