Though the productivity, the quality, and the safety are three principles on any production, the safety seems to go after other two-productivity and quality, which are well-defined and have been studied theoretically and practically in the shipbuilding field. The safety is somehow vague and ill-defined, because it mainly depends on the human factor. However, Japanese shipyards have been full of the elder people, and are liable for keeping the safety and health to them. In this paper, the accidents in Japanese shipyards are reviewed and it is concluded that the accidents of falling and tumbling have occurred frequently : falling from the higher place and also tumbling down the stair. Then, these accidents are picked up, and the human task simulation was carried out using a virtual human model based on biomechanics and ergonomics ; the static strength prediction on human body and the low back compression analysis. As a result, it was understood that the torque on the ankle became greater at the work on the higher position and also on the vertical ladder, and the optimal inclined angle of the ladder was approximately 75 degree.