The number of foreign workers, which has increased since 1989, can be classified into industrial trainees and illegal migratory workers. As of January 1995, the official number of foreign workers reached 49,805 according to the Ministry of Labor. But the real number is estimated to be around 100,000 and industrial trainees are 22,583 among them. The stress induced by the culture shock, 3D (dirty, difficult and dangerous) working conditions, and illegal status of the foreign workers is greater than that of regular Korean workers. By using a psychological well-being index (PWI) measuring stress on 144 foreign workers, it was revealed that 68 people experienced "high risk stress", 76 "latent stress", and the average score was 62.8. The overall stress level was very high. Considering the distribution of high risk stress group and latent stress group by socio-demographic factors, the percentage of high risk stress group was higher among workers whose contract periods are less than 2 years than among workers whose contract periods are longer than 2 years. And the percentage of high risk stress group was higher when the number of workers at factory becoming larger, and also higher among workers who can not communicate well than among workers communicate well. After having a multiple stepwise regression analysis to find the socio-demographic factors which influence the PWI score, we found that the PWI score goes higher when the contract period is becoming shorter and the work hours is becoming longer, and these two factors are able to explain the score to the level 16.3%.