Objective: We investigated the association between job stress and insomnia in a large nationwide samples of Korean workers. Methods: In this cross-sectional study, a total of 8,155 workers from a nationwide sample were recruited. We surveyed the subjects' socio-demographic and work-related characteristics and seven subscales of occupational stress using the Korean Occupational Stress Scale Short Form. Each subscales of job stress was dichotomized into higher or lower group by respective median scores. Insomnia was defined as having at least one of the three sleep symptoms. we performed multivariate logistic regression analysis to identify association between job stress and insomnia. Results: We found that individuals with relatively high job stress experienced insomnia significantly more frequently, and the significance was maintained even after adjustment for confounding variables(high job demand: OR 1.30, 95% CI, 1.14-1.47; insufficient job control: OR 1.13, 95% CI: 0.99-1.29; inadequate social support: OR 1.30, 95% CI, 1.14-1.47; job insecurity: OR 1.25, 95% CI, 1.11-1.44; organizational injustice: OR 1.27, 95% CI, 1.12-1.44; lack of reward: OR 1.18, 95% CI, 1.04-1.34; discomfort in occupational climate: OR 1.38, 95% CI, 1.22-1.57; total job stress: OR 1.45, 95% CI, 1.28-1.64). Conclusion: This study suggested that job stress is possible risk factor for insomnia and that particularly discomfort in occupational climate and inadequate social support have more strong relation to insomnia in Korea.