The object of this study was to investigate the characteristics of a psychological stress reaction scale for employees on the basis of Item Response Theory (IRT). A total of 3,808 employees from three companies underwent the Job Stress Scale Revised (JSS-R) version in order to measure several levels of psychological stress reaction. An examination was conducted using the graded response model to evaluate the parameters, discrimination, and the level of difficulty regarding each item. The obtained findings revealed that certain items for determining depression were superior in terms of both discrimination and difficulty as compared to others for evaluating psychological stress reactions. However, items such as “easy-to-get-angry” might not suitable for measuring workers’ potential psychological stress reaction.