The purpose of this study is that we grasp the value of mental workload for pilot trainee (PT) using a heart rate monitor when they drill in a ship-handling simulator, and that we evaluate the effectiveness of the simulator to supply the place of a real ship based on a trend of the mental workload. The R-R interval data of subjects with a heart rate monitor have accumulated while they train for three months. The data is processed by Spline function interpolation and MEM (Maximum Entropy Method), and then we calculate LF/HF value of the data. The calculated value evaluates mental workload; we originally set a standard value and some values over the value show subject's stress condition. We summarize the number of times of subject's stress condition, and find the trend of their mental workload compared with the events of simulator scenarios for ship handling. Finally, we analyze a period when subjects feel stress, and simulator scenario where they are not good at ship handling.