The effect of wind velocity on the heat transfer coefficient of the air gap between pieces of cloth and a glass bottle surface around a bottle side was measured as a model of an air gap within clothes. Resistance of air flow through a sheet of cloth was also measured for the cloths used in the above measurements. When cloth having large air flow resistance R_F > 400Pa･s/m is put on the bottle, the heat transfer resistance of the air gap, which is in inverse proportion to the heat transfer coefficient, is not affected by the wind velocity and agrees with the theoretical value. For R_F > 240 Pa･s/m, the heat transfer resistance decreases with an increase in wind velocity, and the decreasing rate is promoted by a decrease in air flow resistance of the cloth. The following results were obtained by using the parameter u*(=u²/R_F ) of wind penetration through a sheet of cloth : the heat transfer resistance of the air gap is not affected by the wind velocity for u* < 0.012 m³/(s³Pa), and decreases in proportion to u ^*-35 for large value of u ^*. As the air flow resistance of cloth decreases below 18 Pa･s/m, the heat transfer resistance of the air gap becomes smaller than the theoretical value even when there is no wind. This is due to air flow through the cloth by the natural convection. An empirical equation to estimate the effect of wind velocity on heat transfer resistance of the air gap was obtained.