To investigate the effect of thermal environment and the ventilation rate on productivity, a subjective experiment was conducted. The conditions were the combination of thermal environment: operative temperature of 25.5°C and 28.5°C; and the ventilation rate: 11m3/(h•p) and 90m3/(h•p). Eleven subjects participated in a 350min exposure and worked on three-digit multiplication tasks for 180min. The percentage of dissatisfied with air quality was higher in the higher temperatures and in the lower ventilation rates. The performance of the task was not significantly different among the conditions. The increase of the level of fatigue was more in the higher temperature condition. Correlation between the percentage of dissatisfied derived from perceived air quality and the fatigue level was obtained. The relationships of the task performance and the satisfaction vote of the indoor environment and the level of fatigue were obtained.