The performance decreases as the workers get older and the degree of decrease in the performance shows a marked difference depending on each individuals. On the other hand, the older workers tend to have better ability to adapt to the new working environments and expert skills. Our purpose in this paper is to focus on the analysis about this conflicting situation, thereby important informations are applied in designing working conditions of older workers. Experimental results show that the expert skill of the aged workers can be improved through the effective use of their experiences, therefore some operation can not be influenced by age.