Abstract 1. 1. The purpose of this research was to study the relationship between indoor environment and fatigue by analyzing office workers' fatigue and evaluation of indoor environment according to occupation. 2. 2. This study concerned office workers' fatigue (before and after work), questionnaires on indoor environment, and measurement of the physical environment. The subject (562 people) were businessmen, interior designers, and salesmen. 3. 3. The result of this study showed that there was a high correlation between the office workers' feeling of fatigue and the office environment. 4. 4. This research demonstrated that the workers of each type of occupation responde differently to similar office environments.