The characteristics of mass transfer accompanied by heat transfer for humidification of air were experimentally investigated by using a vertical ejector with a water jet. The values of volumetric coefficient of mass transfer in the gas phase, k(c) a increased with increases in the mass velocity of air, G(I) and liquid, L-I, and were proportional to G(I)(1.29) and L-I(0.49) in a case of single nozzle. Moreover, the relationship between the values of volumetric coefficient of heat transfer in the gas phase, hca and the operating conditions was investigated in the case of a single nozzle. As a result, an empirical correlation by which the observed values of hca can be predicted within an error of +/-15% was obtained.