In order to analyze the relationship between heart rate variability (HRV) and the flight tasks of pilots, HRV of various mental and physical work stresses were investigated. For the physical stress on the treadmill, S.D. of heart rate sequence showed a minimum value at medium stresses and remained there until the maximum stress. However, the centrifuge acceleration test presupposed special physical stresses, and S.D. was almost same as the resting findings. In the tracking tasks, which presupposed maximum interpretative actions, the increase in the mean heart rate (MHR) was small with the S.D. increased a greater amount than for resting results. Consequently, preflight checks and level flight phases presupposed medium interpretative actions and mental stress with reserve capacity. Takeoff and landing phases were considered as both high interpretative action and high emotional stress situations. Acrobatic and gunnery training flight phases were considered physical load, strong interpretative actions, and emotional stress tasks.