Carbon dioxide(CO2) removal from exhaust combustion gas and biogas is recognized as an important technology to CO2 reduction. We are developing a new technology of CO2-removal with a hollow-fiber gas-liquid contactor. In the contactor, the gas flows in the lumen side of hollow fiber, and liquid in the shell side. The gas-liquid interface is formed right outside of hollow fibers because the hollow fibers used are hydrophobic and microporous. The contactor contains a lot of hollow fibers which internal diameters are 320μm, and can produce huge gas-liquid interface area per unit volume. It is so efficient to transfer carbon dioxide between gas and liquid.To confirm an overall mass transfer coefficient (hereinafter referred to as K), the following experiments on carbon dioxide transfer in the laboratory were made: In the soli-recovery test, an inactive gas swept carbon dioxide from carbonated water. In the soli-supply test, a mixed gas contained carbon dioxide contact with static water excluding carbon dioxide, and with agitated water. In the supply-recovery test, a mixed gas contained carbon dioxide contact with static water and an inactive gas swept carbon dioxide from the carbonated water concurrently.In each test, the water was sampled from the contactor, and the concentrations of dissolved carbon dioxide were measured with a gas chromatography. Using mathematical model of the test equipment, the value of K was calculated. These results showed that K depends on ‘water temperature’ and ‘water flow’ without relation to a flux direction and the distance between hollow-fibers, and the water flow system was more effective. Comparing with another technology(packed tower), it was proved that the new one had large dominant CO2-removal forces.