Temperature control for an air-conditioner is an important design variable. Ergonomic studies on the thermal sensation in a normal room temperature are relatively few while many studies are available for the thermal sensations in extreme warm/cold conditions. The objective of this study is to find out factors which affect the cutaneous thermal sensations and so to propose a new cooling control procedure for an air-conditioner using JND (just noticeable difference) values of cutaneous thermal sensation. An experiment to find out JND values of cool and warm thermal sensation was conducted using 13 subjects. Skin temperature, corresponding room temperature and temperature change rate were measured using 297 thermocouples uniformly distributed in a thermo-proof room. Subjective ratings on thermal sensation and thermal comfort were also evaluated. JND values of cutaneous thermal sensation corresponding to the skin, room temperature and temperature change rate were in the range of 0.09–0.80°C. Based on the result of the experiment, a new cooling procedure which lowers the temperature rapidly above the JND values of cool thermal sensation and maintains temperature below the JND values of warm thermal sensation is proposed.