The Evaluation of mental workload and performance usually depended on professionals, captain and pilot, who have a lot of experience on board. We are attempting to evaluate a ship navigator's mental workload using a physiological index. The physiological indices, heart rate variability (R-R interval), nasal temperature, and salivary amylase, are good indices for reading the mental workload in ship handling. In addition, we have found a possibility of salivary as a good index for evaluating the navigator's mental workload. The salivary is expected to have a specific characteristic to represent quick response on the spot and the trend like a moving average. We confirmed the response of students for simulator-based training, and we were carried out the experiments for professionals on a real ship. This research, to evaluate the mental workload of navigators using salivary , is first challenge worldwide. This paper proposes that the salivary is effective to measure navigators' mental workload for ship handlin...