Purpose: The purpose of this paper is to propose that the measurement of salivary amylase activity is an effective index to evaluate the stress of a ship navigator for safe navigation training and education. Design/methodology/approach: Evaluation comes from the simulator and actual on-board experiments. The subjects are real captains who have unlimited licenses and cadets who are senior students at Kobe University, navigation course. Stress is evaluated for several situations where a ship navigator makes a lot of decisions, in this case in a narrow passage, entering a port and leaving a port. Findings: Salivary amylase activity occurs when a ship navigator makes a decision regarding ship handling and collision avoidance. By measuring salivary amylase activity when a student is under duress, cadets' ship-handling training can be evaluated while onboard a vessel. Research limitations/implications: Future research will develop cross-indices with the salivary amylase activity and other physiological indices (nasal temperature and heart rate variability (R-R interval)), complementary to each other. The salivary amylase activity registers the stress quickly on the spot. Then the nasal temperature and R-R interval registers the trend and the quick response to the stress (mental workload). Practical implications: The paper describes an effective index which is useful for evaluating a ship navigator's stress for safe navigation. Originality/value: Ship navigator's skill and cadet's on-board training have been evaluated according to performance and a questionnaire as a quantitative evaluation; moreover, stress is evaluated using salivary amylase activity. (Contains 2 tables, 6 figures and 3 plates.)