There have been large explosions at some chemical plants recently. Accidents in chemical plants have been caused mainly by servicing for maintenance. There is a need to find a key target for effective injury prevention in maintenance. In this paper, facilities were selected as a key target and the risk priority numbers of the facilities were calculated in order to prioritize preventative measures. The research method was based on the followings; the list of the facilities is found through injury analysis. Then, the risk of each facility was calculated by the frequency of accidents and the working day loss through injuries. In addition, the risk of the facilities was calculated again by the frequency and the severity based on knowledge and experience of experts. As a result, the facilities in chemical plant maintenance are ranked in order of high to low risk priority number; reactor, dryer, tank lorry, etc. In the future, special measures and attention should be directed according to the risk priority number during the maintenance of chemical plants.