The relationship between sleep time and working conditions was studied in office workers, from the aspect of health promotion. Data obtained from health checkups conducted on 1366 office workers, including life-style and working conditions, were analyzed. The subjects were divided into three groups: group 1 (less than 5 h of sleep per day), group 2 (5–8 h of sleep per day), and group 3 (more than 8 h of sleep per day). Blood biochemical variables showed no differences among the three groups. The percentage of subjects in group 1 who worked overtime was significantly higher than the percentages in groups 2 and 3. In conclusion, the amount of sleep time is associated with the amount of work done by office workers.