The heat and the mass transfer rates into air from the wetted cotton cloth put on a glass bottle were measured with two experimental apparatus, in which water was supplied to the cloth by using micro-tubes of 0.4mm OD. Hot water having a temperature of 37℃ was circulated through the bottle in one apparatus, and the mass transfer coefficient for various air temperatures and humidity was determined from the vaporization rate calculated with the amount of supplied water to wet all of the cloth. In the other apparatus, the heat transfer rate was calculated from the decrease in the temperature of hot water within the bottle, and the mass transfer coefficient was determined by subtracting the thermal heat transfer rate from the heat transfer rate. There was no observable effect of the water vaporization on the heat transfer coefficient of the air boundary film. The correlation between Sh/Sc^1/3 and Ra for the water vapor transfer under natural convection agreed with that between Nu/Pr^1/3 and Ra for the thermal heat transfer, which indicated that the mass transfer coefficient of the air boundary film for the condition without wind can be estimated from the convective heat transfer coefficient. It was also confirmed that the value of Sh/Sc^1/3 under wind condition coincides with that of Nu/Pr ^1/3 .