Gas absorption enhancement of gas-liquid slug flow by adding non-porous fine particles into the liquid phase was investigated. A glass tube with a millimeter-size diameter was used as the flow channel, and the gas and liquid slugs were air and distilled water, respectively. When the absorption rates of oxygen with and without the addition of non-porous silica fine particles in water were compared by the liquid-side mass-transfer coefficient, k(L), the rate with particles was enhanced and increased as the concentration and diameter of the particles increased. This is because the frequency of particle circulation in the liquid slug increased at higher concentration, and the larger particles caused stronger disturbances at the boundary layer at the interface on the liquid-phase side.