The implicit attitude toward violations is regarded as a contributing factor in those violations. We applied the Implicit Association Test (IAT) to measure this attitude in nursing. This study examines the IAT's validity and reliability. In experiment 1, we conducted IAT and a scale of attitude toward safety for medical staff (Kamizono, 2000) for 71 students from a university of nursing. Validity was demonstrated from a difference of the reaction time between the blocks of IAT and a significant correlation between IAT score and the score of scale. Reliability was indicated by dispersion between trials. In experiment 2, we conducted the IAT for 51 medical staffs who serve as risk managers in a hospital. The IAT's validity was demonstrated from a difference of the reaction time between the blocks of IAT and reliability was indicated by dispersion between trials, too.