OBJECTIVE: This study evaluated the cost for occupational health and safety in manufacturing factories in Korea according to the factory's size and the industrial classification. METHODS: The costs to prevent occupational injuries and promote the general health of the workers were calculated by using the data of The Occupational Safety and Health Survey in Korea in the year of 2005 and the data of the Industrial Accident Compensation Insurance (IACI) premiums at the same factories for the year of 2004. RESULTS: The mean cost per one worker was as follows: 990,000 won for the factory with 5~49 workers, 869,000 won for the factory with 50~299 workers and 1,773,000 won for the factory with more than 300 workers. In the factories with 5~49 workers and 50~299 workers, the premium for the IACI was the largest portion of the cost (62.8% and 52.8%, respectively) and the cost for gear to protect workers from dangerous machineries was the next biggest portion of the cost (20.1% and 19.1%, respectively). The largest portion of the cost in the factories with more than 300 workers was the premium for the IACI (37.5%). CONCLUSIONS: The investment costs to prevent occupational injuries and to promote the general health of the workers were very diverse according to the size of the factories and the industrial classification. To reduce the occupational injuries and to promote the general health of the workers, systematic and continuous approaches to evaluate the investment costs for the occupational health and safety are required.